Golf should be the easiest sport in the world -- the ball doesn't move. All you have to do is concentrate and do something you have practiced.

Similar thing goes with professional athletes. Why does their performance vary so much week to week, game to game?

Take Eli Manning. Never wins the big games, but now seems like he may start to.

http://sports.espn.go.com/nfl/playoffs07/columns/story?columnist=pasquarelli_len&id=3184238

What is it that causes a person to one day be able to do something and not the next?