People who are 30+, what career moves do you regret in your 20s and/or what choices are you happy you made?

Staying where you aren’t happy.
It is rare these days that loyalty and seniority are rewarded how it was depicted in popular media. These days the best way to make more money is to leave and find a new job.
Never let anyone make you work hard, work hard for you and for your goals.
In my 20s I didn’t realize how much more valuable my time was compared to the money I was being paid to give it up. The most valuable thing you have is the rest of your life, you’re being paid to give someone else your life for a time.
- Thank you for your insight!

- Funny, I actually regret sort of the opposite. I went into a couple startups and small companies at first, and I wish I had gone a more resume impressive route.
  
  Grass is always greener on the other side
- Sorry to hear, hopefully you are in a better place now
- I don't regret working for Amazon... for the most part. But that place also messed me up for years. Now i can look back on that place as a learning experience. I hope you get there too.
  Would i do it again? No.

I regret staying in my first job too long thinking I’d advance internally.
- This is by far my biggest regret. Stayed for 6 years with below average pay, believing in the fake promises.
- Yeah, long gone are the days of company loyalty for the sake of advancement and security. The fastest way up is out, not through the glass ceiling.

I'm happy that I switched from electrical engineering to software engineering. I feel like the prospects are better and still feel that way even though things are rough right now.
I regret being scared during my first 5 years as a software engineer. I've stayed in jobs too long. Going forward, once I get that feeling that I've outgrown a role I know its time to start looking for the next thing. No more lingering for that extra year. I'm in my mid 30s and so am feeling the age pressure to make my next couple big moves soon before I'm looked at as too old to be an "IC with a bright future" haha.

Your health comes first.

I have too many...I'll pick my favorite lessons as they're all kind of related
Don't stay at a job too long. Eventually, you'll be training a new hire that makes more than you and they'll probably be your replacement.
It only takes a couple promotions before your career development stagnates usually because you'll always be seen as the person you were when you started. Get a new job elsewhere with a title higher than the place you left and that becomes your new baseline. Repeat every few years.
If you want to earn more money, get a new job. Bonuses magically dry up. And your yearly performance increase won't ever keep up with inflation. Even lateral moves at a different company can mean decent salary inceease as market rate changes over time. (This doesn't always work with a lateral move so shoot for a higher position).
Don't sweat the specifics for job requirements in postings. They're not expecting someone that hits every bullet point. That would be dream candidate that doesn't exist. If you're at least familiar with what they're asking for and can pick it up, then you're good. Most of the time you're trained on the job anyway. Just demonstrate you're competent.
(Oops didn't realize this was a CS / programming community. Hopefully some of this still applies)
- Oops didn't realize this was a CS / programming community. Hopefully some of this still applies
  Great insights. It all still applies.

There's one thing that I regret to this day - going fulltime right after school.
I studied gamedev, and we had a game going on pretty strong, which we were determined to finish in our free time. We were working on it with my roommate and a classmate, who is in general a pretty creative person - he writes LARPs for one group, is leading a amateur theater group, leads our game development team, masters RPGs, etc. He also works as a programmer, just like me.
When we finished school, he decided to stay working part-time, two days a week, and continue living in the student's appartment with our 3 more friends. Keeping his expenses as he had before during school, and focusing on his creative projects in the free time. Because as someone without a car, family, and i a shared household, on a programmers salary, you can get by pretty comfortably.
I, on the other hand, decided to go full-time. And boy does it sucks to get energy for hobby projects after you've spent 40 hours a week of working. Sure, I had more money - but the fact that after paying all my necessary expenses (which I was able to do even part-time), I was left with 3-4 times as much money didn't really help me at all. Sure, I had financial security, I could buy whatever I wanted and didn't need to pay any mind to my spendings, but was it worth it? I'm more and more conviced that it wasnt. I had to start forcing myself to work on my hobby projects that I've loved before. I started postpoing it, and was stressed by trying to shove that much work into so little time.
The money didn't help it at all, especially since I didn't really need them.
He's still working on plethora of projects I'd love to join in, but my contribution is getting less and less reliable, and more and more stressful for me, because the 8 hours of job work per day will just suck all energy out of you, especially since the projects are usually also programming related.
If I could change it, I'd never start working more hours than I need to comfortably get by, even with a little bit of frugal lifestyle. It's not worth it, and the stress caused by trying to overwork myself with the hobby projects, missing deadlines with both work and said projects, has taken a great toll on my mental health in the past 4 years we've finished school. In fact, I didn't even manage to finish my diploma thesis, after postponing it for three years, so I don't even have the Masters even though I did finish the state exam.
So, if you can, limit your work hours as much as you can to get by, and work on your own projects in the meantime (if that's what you want). The money are not worth it.
(I'm actually finally planning to go back to part-time, and take another Masters in game design this year, and probably stay at that, so I'll see how it goes. But seeing the difference between my best friend and me, where our paths diverted exactly by this, he's turned out a lot better than I did after those three years.)

I'm not 30+ yet but getting close and there's a thing I already have so
I've stayed at one place for a bit too long, wasted time not learning new skills and now that I'm looking for a new job, my resume looks a bit sad and I'm not sure the company-specific PM skills I gained at one place are going to be useful enough in a different one

Regret:
Not taking care of my health. Too much sitting in front of a computer, not enough walking around. Too much junk food.
Not keeping track of people after leaving their immediate circle (team changes, company changes, leaving college, etc.). Literally every opportunity I've had has come from somebody I know, yet I've done a poor job of keeping a network socially. It's not that hard to chat with people every few months, but I didn't initially put enough effort into it.
Happy:
For me specifically, staying at my first job for a long time was really good. It helped me grow, and the company was pretty good with salary increases.
In contrast to my regret, I did a good job of making friends with teammates and getting along with people I work with the most.

I never worked in my chosen field and fell into software development instead.
I wish I could say it made me happy but it's quite the opposite. I feel out of my depth every day and I've never been promoted or such, and I've been with the company for almost ten years.
I'd go do something else but I don't really have any skills worth mentioning so I guess I'm stuck here until I get fired or am eligible for a pension (not gonna happen btw, there will not be any pensions for gen y and on.
So I just feel inept and stupid every day. At least it keeps a roof over my head.
- Apply for govt positions. If you hate your job and are underpaid anyway, you can have an actual career, pension, and maybe help some folks along the way. I'd have to take a fifty percent pay cut to go into government work and I'm too old to reap the benefits, but sometimes I regret not taking that path. I've known a lot of happy people in government work. Not that it's not frustrating as fuck in some ways, but it kinda sounds like that's not really a downgrade for you.
- I wish I could say it made me happy but it’s quite the opposite. I feel out of my depth every day and I’ve never been promoted or such, and I’ve been with the company for almost ten years.
  I've learned recently to really ask for the promotions and recognition I feel like I deserve

Not walking out the door when I should have. That's a tough call to make and the conventional wisdom is that you shouldn't quit your job before you have another one lined up, for understandable reasons. You have bills to pay.
The worst job I ever had was as a manager for a large utility. One time, we got quite a bit of snow. I didn't have 4 wheel drive so I asked my boss if I could take a company truck home. He said that was fine.
The next day, he called me into his office and told me I was in trouble for taking a company truck home. I was very confused and responded that I had asked him about it before I left and he said it was fine. Turned out that motherfucker had been asked by someone further up the ladder if he signed off on it and instead of just saying, "Yep, I told him it was fine." He proceeded to lie his ass off and then pretend like we never had that conversation.
He showed me what kind of person he was and what kind of company I was working for. I should have immediately handed him my badge and walked out the door but I didn't. I stayed there for a few years after that. That was the tip of the iceberg on top of a completely toxic shit hole. The worst I have ever seen.
Never let someone try to take your dignity away from you and don't spend any longer in a toxic workplace than you absolutely have to.

Being loyal to a start up. As soon as I got those shares , should have cashed out and moved on asap.
Change jobs as soon as you can, easily blame it on being young and they never held it against me when I finally did learn that. And since you’re in your 20s, they will never let you retire there anyway. So why stay?

Staying in jobs that made me miserable for longer than I could have.

Not cultivating my network.
- Okay, I will bite the bullet, what and how do you suggest?
  
  Keep in touch with former colleagues who you’d want to work with again. At least touch base once a year, get lunch together if you can. Talk about what you’re working on. A network really helps if you ever decide to go contract or start your own thing.

I regret staying at some jobs 2+ years and having my tech skills rot.
I also regret not joining companies that consult me out to clients sooner. It led to a massive increase in my own confidence and my technical skills across a lot of industries and technologies.
I also regret trying to be loyal to some company. It never pays off.
In the last 6 years I've averaged a job change every 6-8 months and have increased my base salary from $125k to about 4x that.

Regret:
Not getting into web development sooner. I spent a good chunk of my 20s trying to be an animator. I should've seen that it wasn't going to work out sooner, and I even had friends who offered me web dev gigs. I eventually got one, but I could've got one probably 10 years earlier.
Like some others have said, being loyal to startups. They're never going to be loyal to you, so why bother being loyal to them?
Really, the two previous points could be combined into a somewhat related point: don't keep white-knuckling through on some career path if it's looking increasingly bad. The reason I used to keep white-knuckling is I believed perseverance in the face of adversity was the most important thing. While I agree perseverance is important, it's even more important to find that line between pushing yourself for a good career, and pushing yourself for something that may no longer make sense. It's not always easy to let go of something that you've already invested time and energy into, but sometimes its the best way forward.
Happy:
I developed frugal spending habits, largely due to my pseudo-artist lifestyle. While that isn't directly a career thing, I'd argue reducing my spending allowed me to last without income longer, which let me be more choosy about which job I got next.
I tried anything that interested me. This included programming - which ultimately became my career.
- "While I agree perseverance is important, it’s even more important to find that line between pushing yourself for a good career, and pushing yourself for something that may no longer make sense. It’s not always easy to let go of something that you’ve already invested time and energy into, but sometimes its the best way forward."
  This is actually how I feel about WebDev now. It doesn't seem worth it to start now with the future so uncertain and with all these "no Jr dev" hiring practices I've been reading about, plus my stupid fucking brain can't find any interest in the work at all... I swear my stupid fucking brain is only interested in things you can't make money with...
  
  This is actually how I feel about WebDev now.
  Yeah I have those days too. I have about 5 years' experience, but after thousands of applications, I'm only getting a few replies.
  swear my stupid fucking brain is only interested in things you can’t make money with…
  Yeah I hear ya. I have lots of interests that are almost guaranteed not to make money.
  
  Ah yeah same lol. I managed to get about 5 years' worth of a web dev career before this bottomed out.

Bad idea: Tempted by a silicon valley startup because that's what all the cool kids were doing. They were style over substance.
Good idea: leaving my otherwise excellent first real job. I owe them ( slidebook.com ) a lot. I wouldn't be half the developer i am now if they hadn't given me the environment to approach software as a science. That said, leaving was the right call.

I should go around asking the elderly about their regrets too tbqh

Spent pretty much my entire life working from 16 onward. Financially, I'm doing alright, I have enough money that I could pay off my student loans right now and not be on the brink of ruin.
I'm so burnt out that I'm pretty sure I'll kill myself when the money runs out after I get fired. I do not have the emotional wherewithal to start looking for another job in the age of video recorded interviews and 50-question corporate ball-gargling quizzes. I don't want to jump through hoops anymore just to be able to live, to the point that I would actually rather die than try to get another shitty day job. I sort of hope I don't get fired, but at this point I'm too tired to care all that much.

Wish somebody had pushed me more into practical things instead of letting me think that being "book smart" was all I was going to need.
That led me into thinking that I NEEDED to go to college, which meant that my poor self did stupid shit to get the money to go to college. Only after spending 8 years to get money and try college (after spending all the money) did I realize that I should have gone into some tech/vocational training thing. (Mechanicing, HVAC, plumbing, etc.)

After university, I was a volunteer teacher in Africa for 3 years. Then I went and taught English in Japan, and after that started working as a software developer.
If I had stayed in Canada and gone straight into a typical chemical engineering job, I would certainly be a lot better off in financial terms, but the whole reason I didn't go into it was because I found it soul crushing.
One of my engineering classmates went into theater production, another did a master's in English, and a third went to medical school. Clearly I wasn't the only one having misgivings.

- The experience you get in open source and being able to talk about it in interviews can really help once you get there, but it doesn't help get the interview and you have to really apply yourself to get something valuable out of it. My GitHub CV is full of a bunch of bullshit I started and spent at most a month on before abandoning. Of course I've worked on a project for two years now and I wasn't even allowed to include it because there's no boss or company or address - just me and another guy from Europe I met online working on a passion project that probably neither of us have the drive to turn into a business.

A few years out of college I was making $X, and was simultaneously approached by two companies. The first was located just outside of Paris, for $X+n (small $n). The second was about 50 miles from where I lived in Oregon, but was $2*X. I chose the second, which led me on a career development path that worked out well for me financially.
I wish I'd taken the job in Paris. It would have set me back a few years, financially, but in retrospect, I'd have valued the experience more.

Best decision I made was taking an internship. I wasn't really looking for one, but through some connections, one basically fell in my lap. It was in old tech I messed with in high school, so I was reluctant, but getting real world programming experience was fantastic. The team was great and I helped solve some interesting problems on a small project of theirs. They kept me on as long as they could (>1 year). I think people can be way to idealistic, especially when starting out. Go get a year or two somewhere, anywhere. You'll have a ton more marketability and control over where you end up with experience and professional references.
Biggest career regret was waiting around afterwards for a time to try to get hired on at that same place. Not a ton of programming jobs locally and I wanted to continue my work there, but the company went through semi-frequent growth/shrink phases, and my team wasn't able to get me hired in, though they did try for a while. There were plenty of other good things happening in my life during the down-time after this job and before the next, so it's not really something I regret, but I definitely won't wait on a company like that again.

I regret not taking my suspicions that I had adhd more seriously.
Ie I suspected I had adhd when I was in my early 20s now that I'm in my mid-late 30s and getting sorted out, I can sometimes daydream about how different my career could have been if I'd been firing in all cylinders the whole time. I don't day dream for very long though, I've got things to do.
- I feel that I also do. Curious what route you took to manage or treat the ADHD. I was recently suggested MEMS
  
  My family doctor referred me to a specialist clinic.
  Specialist diagnosed me and made some suggestions to me family doctor. Some medications, some counseling some organizational stuff.
  The organizational stuff is what really helps but it's just the 'get organized' stuff that everybody recommends. but with the meds I'm actually able to do it.

So warm topic.
I have almost 40+ and what I know definitely that nothing can be true thing in our job. Today you on the wave, in 10 years this wave is deprecated.
I can feel self pity about different desicions but when look at my path with sober mind I see that nothing can be deffirently.
The main thing is energy. If you have it you do not care how old are you. But industry is full of bias about devs age. So let's they go hell.
I am definitely happy that decided to learn programming in my 13.
I regret that didn't pay attention enough to math and physics to have a more interesting background than just software development. And now I am learning, returning to the roots. 😄

I'm glad I worked at a startup without benefits while I still had coverage from my parents. I'm also glad I realized I prefer medium-sized companies before I lost that coverage.
I regret the mentality that kept me at shitty jobs for five years. Being afraid the grass wouldn't be greener left me in a cycle of getting mad enough to polish my resume and send it out, but then never really following through.