So, I should note that I don't indicate that you should forget everything you know
Just that "we have to forget the pain
of past failures".
If you are a sports fan, you can think of it just like a receiver. They have a difficult job in that they have to concentrate on the ball coming to them and protecting it once they catch it, but "forget" that they are about to be hit by a small freight train sized opponent, and that the last time they did it hurt really so bad they dropped the ball and lost the game.
They still should remember the lesson of that failure (that they have to protect the ball), but not dwell on the failure or they will do everything they can to not be in the position to even catch the ball so they won't get hurt.
Failure is a big part of the educational process (http://www.simple-talk.com/blogs/2011/04/16/what-counts-for-a-dba-failure/) but failure can lead you in two ways and fear will hopefully not be the one you choose.