Many top athletes have been in this nightmare scenario: They are facing a career-defining contest or competition, and are very well-prepared, but at some point in the event, their performance deteriorates to that of a beginner. But why does this occur?
Thousands of hours of training and practice has prepared these experts to perform complex tasks. In fact, the tasks have long since been handled by their implicit brain system, so they are done automatically and can be performed simultaneously.
The phenomenon of failure when the stakes are highest is called choking, and it occurs when the athlete has to perform a complex but familiar task under high pressure. This happens because as you know, under pressure the brain transfers control of any task to the explicit brain system, which unfortunately cannot do many things at once. Thus the athlete is no longer able to perform complex tasks and chokes.
To avoid choking, athletes have to convince themselves that the competition is irrelevant, as this will lower the amount of pressure they feel.
Actionable advice:
Before facing a big competition, try to put things in perspective by thinking of things much more important than the contest, like your relationships, health or your family. This will help you feel less pressure, which will allow you to use your implicit brain to perform the tasks.
Therefore it seems that to excel, top athletes must practice as though their chosen sport was the most important thing in the world, but then downplay this importance when the stakes are highest.