You have done the training, you know how to swim your race, and then you walk out behind the blocks and your head fills with lane four, the clock and what everyone will think. The race is half over before the whistle, and not in a good way.
The gap between training times and race times is almost never fitness. It is nerves without a routine, focus without an anchor, and a pounding heart read as a problem instead of fuel. All of those are skills, and skills can be trained.


