I live in the UK, so I get 25 days off work, and I take full advantage of that, I rarely do staycations.
I'm about to buy a property and I'm deliberately going to get a mortgage where my monthly payments are not as much as I can possibly afford, but a bit less. This means that it will take me longer to pay it off, and overall it will cost me more, but I will have more disposable income today to spend on life's pleasures.
I don't have kids and don't plan to.
I stay physically active, just simple going to the gym 5-6 days a week. And I think this is really important. It will keep your body in shape and by the time your 60 or 70, you'll be able to do much more than your average peers who spent their middle age doing office jobs followed by evenings in front of the TV. And here, instead of my 41-year-old self, I'm going to use the example of my mum. She's turning 70 next year, but it was only when she was 68 that she started taking swimming lessons and she got to love it. It was also around that time that I floated the idea to her "why don't I take you for holidays to New York". She was all "no, no, I'm too old, it's too much walking, you took me for a holiday to London when I was 55 and I was totally exhausted, I wouldn't be able to do New York at this age." Now that she's had over 1.5 years of almost daily swimming (and cycling, she's also a keen cyclist) - she said yes. She said she's feeling perfectly fine doing long walks, she's more energised, and she already gave me a list of what she wants to see in New York.
Other than physical activity, scientists seem to agree that the other two pillars of long and healthy life are good sleep, and good diet. For the former, I recommend reading Why we sleep by Matthew Walker. And good diet means varied diet, vegetable-rich diet, and low-calorie diet (too many books agree on that for me to recommend a specific one).
Simple doesnt necessarily mean easy to accomplish. I took it to mean they just go and so something as opposed to some structured, unwavering plan or training so hard they cant walk 5 days out of the weak.
Could probably accomplish something similar with 100-200 squats and push ups a day, but going to the gym gives you more variety
Yes, I guess whatever regular physical activity is good. But not gonna lie, during the pandemic when gyms were closed and all I had to stay active was my dumbbells at home, it was pretty much harder to motivate myself to do the limited number of exercises available to me in this set up. Gym does allow for some variety.
I work a full time job. 5 days a week, 8h a day. I don't have many other responsibilities, so it's not that hard. I would say that gym consumes 2h in one day, including traveling to and from (although my gym is like 1 minute off my route to work) changing before and showering after and that includes 60-75 minute workout. Days when I make plans with friends in the evening are trickier but if I stay disciplined, I make it work. Also, I start work at 7 and leave around 3.30, so I'm home around 6pm after a day of work and gym. And as for being drained after work, my job is mainly thinking (I'm a scientist). I don't know what you do, but I can imagine having a physically demanding job can indeed discourage from the thought of lifting some dumbbells after a whole day.
As for motivation, don't have much more to advise than: you just have to force yourself. I guess sticking with it for a few months and seeing the effects is indirectly motivating. Scientists say that will power itself is like a muscle: the more you exercise it, the more of it you seem to have. Every day is an internal struggle for me, fending off the thought "maybe just today... I can skip gym?" Sometimes I cave, but I do manage to make it 5-6 days a week.
Your point about the mortgage eventually costing you more in the long run is exactly what I advocate for. So many moneybros out there advocate for living in squalor so you can both aggressively save for retirement and pay down all your loans.
But life is uncertain and even if you live a healthy life, you never know if you'll just be hit by a car and killed one day.
Life is about maintaining a balance. Sure, save for retirement, but don't do so so aggressively that you ruin your ability to be happy now.