"Think of something you imagine you can't do but would like to be able to do. Now how would you stand if you knew you could do it? How would you talk? How would you breathe? Right now, put yourself as congruently as possible in the physiology you would be in if you knew you could do it. Make your whole body give you the same message. Make your stance, breathing and face reflect the physiology you'd have if you knew you could do it. Now note the difference between this state and the one you were in. If you are congruently maintaining the right physiology, you will feel "as if" you can handle what you didn't think you could before."
-- Tony Robbins in Unlimited Power