Any athlete will agree that the state of mind is a very important factor in achieving the best performance possible. I remember reading about a race in England where a runner one day broke a record and ran the race in under 1 minute. Since then nobody had ever accomplished this time, but after it was shown to be possible a lot of other runners did the same thing. The 1 minute was like a psychological barrier, that had to be broken by a supreme athlete that wouldn't be affected by this psychological barrier.

These barriers exists in all kinds of sport and will affect performance of athletes, but the individual athletes also have their own barriers. Especially in sports where you are constantly aware that you are about to set a personal record. The reason can often be found in the mindset of the athlete, some will begin to think "I can't afford to miss this chance", but the negation in the sentence (the word can't) is not good, because the subconscious mind will only be able to represent "miss this chance" with mental images.

Gregory Bateson once explained this - not in terms of sports but - in terms of animal communication. When two dogs meet how do they agree that they are not going to fight? Dogs don't have a verbal language like humans, so in order for one dog to "tell" the other that this has to do with fighting, it must show its fangs, but somehow communicate that this is what's not going to happen. It is common for hypnotists to give the following example: "Do not think of a pink elephant", what happens when you read that sentence? You will inevitably think of a pink elephant, even though that's what you shouldn't do.

A lot of the knowledge that hypnotists gain through experience can be used to aid someone to improve their performance, the above example is only one example of a limiting way of thinking, that can prevent you from performing your best.