[wludavid]

Think of it as inertia. It's much easier to sit around or to sleep in than it is to get exercise. I don't think running requires more motivation than other sports, it's just more typically solitary, and therefore it's more internal than meeting to play basketball or soccer. If your goal is to be alone, clear your mind and get exercise, then you really can't beat running. But the tradeoff is that you have to be disciplined.