I think it's just hard to avoid doing things by thinking about them. Good luck avoiding touching your face for an hour by saying "don't touch your face." Luckily you can normally focus on doing something else like keeping your hands in your pockets.
I have this problem with biting my fingernails.
OK. I read it. Why do athletes keep making the same mistakes?
Because the concentrated effort needed to "not do something" seems to increase the likeliness that you will do exactly that, especially under stress. For some reason, it seems that it is not the will or intent of the thinker that is important, but what the thinker is actually thinking that controls reflexive actions.
So Zen and Yoda are right again :)
"Do not think anything. Just do."
Well, yeah. I knew that from watching Homer's antics on the Simpsons. This doesn't dp anything to explain why if you incessantly think "Don't do x; don't do x" then you wind up doing x. But maybe I'm expecting too much from an article in the Sports section.