There are 6 key components I have found for high performance....
The first 3 are:
Sounds silly, but getting prepared for the race is what it is all about. Training properly, getting the fitness gains and performance levels where they need to be takes a commitment few are willing or able to give, especially at the highest of levels.
The last 3 are:
Sounds silly again, but perfect preparation is meaningless if an athlete doesn't execute properly on race day. For example, watching the ITU WTS San Diego event here this past weekend, I saw a number of excellent runners go out WAY TOO FAST for the first lap of the run, only to blow up and be beaten by athletes who they are better runners than.
We see a lot of execution errors among amateur triathletes, from pacing to nutrition, and even if they did all the perfect training, highest level of fitness, they become their own biggest hurdle. They likely weren't confident enough in their preparation as well, which brings us back to the first 3.
Have excellent preparation, then execute according to that preparation. They go hand in hand, at all levels, from amateurs to high performance.