Outside of the obvious physical abuse players bodys absorb one has to consider the mental side. I mean when your a NFL player your in the limelight , center stage, everybody wants a piece of you. When you retire, outside of a select few super stars, the world passes you bye. No more center stage, everybody knows who you are etc. You're back to just being Joe Blow common man. That too has to be a big emotional adjustment for a lot of players.