I love to run. So, it's one of the few things that I don't need to look for motivation. I don't look outside and say "Oh gee, I have to go out and run." I look outside and say "I can't wait to get out there." I run about I would say at least 5 - 6 times a week. Generally during the week, I run at lunch time. The whole thing from start to finish takes me about an hour. So, I just build it into my schedule. I feel good about running because it just physiologically makes me feel good. The endorphin level is great. It's kept my weight down. I don't think I have a lot of unnecessary fat on my body, which I think is not only healthy, it looks good and it feels good.
Mostly, I think the benefit for me is a stress reliever because I have a pretty high stress job. I spend about 15 hours a day in my office at the NIH, maybe more. So getting outside in the day and hearing the birds and smelling the grass is kind of a very pleasing thing for me.