Experts once said that the human body was not capable of a 4-minute mile. In 1945 the mile record was set at 4:01 where it stood for NINE years. On May 6, 1954, Roger Bannister broke the 4-minute barrier and setting the record at 3:59.4. Visualizing the achievement was a big part of his training he willed a sense of certainty in his mind and body. Bottom line - having certainty that a task can be accomplished is necessary to you achieving that goal.