If one examines the biographies of some of the most successful people in the world, a common thread among many of them is long periods of deep frustration and pain.
I guess happiness is not as strong a motivator.
I'm not buying it. If you look at successful rulers, that may be right, but I look at a lot of very happy athletes like Elway, Foreman, Barkeley, Woods, McEnroe, etc. and they look as happy as can be.