I was watching the history channel this afternoon and there was a comparaitively scrawny magician in a weight room with a bunch of sweaty weightlifters.
He was explaining to them how everyone has a weak spot
He watched one of them lift a huge amount of weight and when the athlete was done, he asked him to examine a wooden box about 5 x 5 x 16 inches with a handle on top.
The magician then asked the weightlifter to hold it straight out in front of himself with his left hand and then to put his right hand over his left.
Then the magician said when he touched the weightlifter in his weak spot that the box would become very heavy. When he touched the weightlifters forehead, the weightlifter could not keep the box from going downward.
Pretty soon this 5 pound box was on the floor and the weightlifters muscles were shaking. He admitted he was embarrassed. What made his muscles go weak? Why couldn't he keep a five pound box at chest level for no more than seconds?
His mind had been convinced that he could not keep that small box in the air.
Lack of belief is what makes people lose quits
This is why we stress the mind aspect of quitting. You can't do it if you don't believe it.