You need to monitor your goals and you need to see and know how you are doing otherwise you will falter. To prove this point, a man in a pub took bets from people in the pub and challenged one of England’s champion dart throwers that he could make the expert falter in less than four throws – and without interfering in anyway in the throw itself. To do this this, the challenger simply help up a piece of paper in front of the champion’s face, just after he had released the dart – so that the champion could not see how he did – and then he removed the dart before the next throw. Sure enough, the champion’s game went to pieces in three throws. Without seeing – instantly – the results of each throw, he missed the next shots. – Dorothy Leeds

Dorothy Leeds, PowerSpeak, 1988, London: Piatkus, p.8