Keeping me from getting too fat without changing my diet.... Really, I like the thinking and just physical movement a lot, and the feeling you get when you're going fast which is a result of personal effort.

One of my favorite parts of commute is this turn really close to my house that I take on my way back. It's kind of banked and there's a small hill to go down to get to it, almost no traffic, I can see past the curve, so that all allows me to take the turn really fast and I always get a thrill there.