We are first of all brains. Without them we are of little value to ourselves or anyone else. It only makes sense that we would seek to maintain our brains and the body that houses it. When we are well and fit our brains can run, walk, lift and feel and otherwise gather tons of data with which to think.
This article makes it fairly clear that there are things we can do to improve our lives. The article online at lifehacker is an excellent review of things we can do to maintain a physical life that is powerful and balanced. The article is entitled "Top 10 Reasons to Exercise Regularly (Besides Losing Weight) and is worth the time it takes to read it.