Mozart is a good example of a life ruined by nuttiness. His achievement wasn't diminished—he may well have had the best innate musical talent ever—but from the start, he was pretty miserable. He overspent his income his entire life—that will make you miserable.
I have never succeeded very much in anything in which I was not very interested. If you can't somehow find yourself very interested in something, I don't think you'll succeed very much, even if you're fairly smart.