Couldn't have said it better myself...
While running is easy to learn and fairly inexpensive, it also benefits the runner’s mental outlook. Basically, what is good for the body is good for the mind, and psychologically speaking, running has a lot to offer!
You have to wonder at times what you’re doing out there. Over the years, I’ve given myself a thousand reasons to keep running, but it always comes back to where it started. It comes down to self-satisfaction and a sense of achievement. – Steve Prefontaine