In 1954, 25 year-old British medical student, Roger Bannister, broke the four minute mile. Up until that point, it was thought not possible that a human being could achieve such a feat. Within the year following this historic accomplishment, the four minute mile threshold was broken sixteen more times.
What was the difference?
Human beings are a bi-product of their belief system. When we think something is impossible, our expectations drop as does our performance. You become what you think about!