haruki murakami, one of my favourite contemporary novelists, has written a memoir called "What I Talk About When I Talk About Running", the book is due out in august. here's a brief excerpt.
"People sometimes sneer at those who run everyday, claiming they'll go to any length to live longer. But I don't think that's the reason most people run. Most runners don't run because they want to live longer, but because they want to live life to the fullest. If you're going to while away the years, it's far better to live them with clear goals and fully alive than in a fog, and I believe running helps you do that."