It has to become habit. It takes a person 28 days to establish a new habit. So force yourself to do it for a month and it'll just become part of your lifestyle. It's a lot easier if you pick something you actually enjoy. I lift weights throughout the winter, and early spring, but I don't like it very much, so I have to be disciplined when it's time to start. During the good weather I rock climb, do a lot of hiking, ride mountain bikes, and go backpacking. I do enjoy that, so it's never something I need to make myself do. I miss it when I'm not doing it. So the best advice I can give you is to find a physical activity you actually enjoy, and then make time for it. It could be basketball, tennis, karate, chopping wood, whatever. Try different things until you find something.
Turn it into a part of your lifestyle. I got my tennis such that it feels wrong if im not doing it regularly. They say it takes 90 days to make something a habit. Now working on zone 2 conditioning, and hopefully turning it into something more. Good luck!
