This is a good piece in The New York Times on the paradox of success:
Similarly, to succeed in the N.F.L., it is not enough to be strong and fast. Witness all the college players who exhibit all the physical skills they need in the league’s draft who never succeed as professionals. Rather, the best players display a certain manic competitiveness such that they keep playing. The Denver Broncos’ quarterback, Peyton Manning, has won a Super Bowl and made $230 million from football alone, and he looked to be in profound physical pain at the end of last season. Yet with his intensively competitive streak, he intends to come back next season at age 39.
The paradox of success is this: The mental wiring that enables a person to claw to the tippy-top of Corporate America or sports or entertainment or any other field that offers vast wealth is the same mental wiring that most of the time leads people not to retire before they have to — no matter what the diminishing marginal utility of money would suggest.