They'll use phrases like, "Things are going almost too good," as if Murphy's Law would prevent success.
When you reach this high fitness, refer back to it, and have confidence. Trust in your training, your coaching, and your ability to race. Don't expect perfection, that's a pipe-dream. No race ever goes perfect.
The mind is a powerful tool. Think back to all your races, and compare the difference between the best performances and the bad ones. Chances are the one clear difference was the attitude you had on the start-line. If you were worried, scared, and focused on things you couldn't control, you likely did poorly. If you focused on yourself, and approached the line with confidence in your ability, and were excited to test yourself against the competition, you likely performed well.
Make your attitude on the start-line a priority for you, and keep your thoughts positive, and on the things you can control, and you'll see a marked improvement. Don't let your mind sabotage your fitness.