About a year and a half ago I started running. Not sure what drove me to it, but I guess some motivation behind it was as a way to get in better shape/health. I bought myself a cheap pair of running shoes and clothes and started out on a short run.
I remember after the first time, I felt like I was having a heart attack. That's how out of shape I was. After just 2 km I was spent. Then I was surprised how quickly I improved. After maybe the 4th or 5th run I went for a longer run.
When I felt comfortable with a certain distance, I expanded the length of the run.
Finally, above you see the run I completed last week which is also the furthest I've ever ran. Soon I need to start running into other parts of Stockholm if I want to continue. Although I think I'm happy at the current level of running a lap around Kungsholmen (~10km). I try to do this at least once a week, plus a few shorter runs. It really depends on how I feel though. I don't necessarily plan out my runs. I just go with what I feel like.
What I really like about running is that it seems to clear my mind. All the worries go away, because I have to focus on my body instead. In addition, I always get a confidence boost afterwards, because it feels like I've accomplished something. Maybe there's a small endorphine reward involved too.
That said, I also think it's important to keep mentally active. I see so many people who get obsessed by fitness to the point where it governs their lives. For me, the mental aspect has always been more important. Keeping a balance between the two is probably a good way to live your life.