Competitions are won and lost BEFORE they even begin, because of the relationship between your mind, body, and performance.
In other words, WHAT YOU THINK OR SAY TO YOURSELF both before and during your performances goes instantly and directly into your body and touches off some subtle physiological changes. These small physical changes, in turn, significantly affect how well and fast you can swim.
The mental side of your performance is critical. So, never leave this important factor to chance.
This doesn’t mean ‘wishful’ thinking on the day of competition. It means train your mind and body for competing during the regular, smart, and hard training sessions.
Also see: http://www.swimming.org/sport/dealing-with-anxiety-young-swimmers/