I don't know many ambition- ridden people who really enjoy themselves. Even success doesn't seem to still the insatiable, gnawing hunger of their ambition. Ambition is a good gift, but it cannot be all.
There ain't nothing like being in the corner, and the trainer is whispering in your ear and another guy is putting in your mouthpiece. Five seconds to go, the boom! The bell. It's more exciting than looking down a cliff.