You've practiced 100 times, you know what to do, yet there are times when we don't have the courage to trust our training and go for it. All it takes is a leap of faith and you can race the best race of your life. Practicing how to jump out of an airplane is totally different than actually jumping out of an airplane.
When you train, the pressure that's on you is different than the actual performance you are training for. We have the Olympians who train like none other to compete, but once in front of everyone else, the pressure is immense. It takes incredible courage to trust your training and perform to the best of your abilities. Everyone's eyes are on them, a single mistake is not allowed, and because of that, the athletes get a little rigid and can't perform as well. However, when they overcome that pressure and rise up above everything that is pushing them down, they perform phenomenally.
Trust the training, trust your rest, trust every move you make, and in trusting everything, it allows you to perform under those extreme pressures. Overcoming the pressures, you can rise up to an even higher level, making a difference to your performances. The pressure doesn't matter to you anymore, and you're able to put your best foot forward and work hard. A foundation of trust must be built upon the training you underwent. Believe in that training, and believe in yourself.