Concentration is a key component in being able to control your arousal, anxiety, and stress levels in order to swim optimally.
Being able to step up on the starting blocks, block out all noises around you, visualize what you are about to do, and then dive in and do it is extremely important for success all the time, no matter what the meet or how you feel.
Controlling your breathing rate and lowering your arousal level (along with your heart rate) will allow you to focus and concentrate. Some swimmers are just naturally born to be really good at this, but, it can also be taught and practiced. This should go hand-in-hand with the visualization of your races.
Whenever you do your imagery, you first must close your eyes, slow your breathing, control your heart rate, and get yourself ready to imagine. Once you are content on moving on, then start your visualization. As you practice this, you should be able to take less and less time to calm yourself down, get your arousal level at it’s peak performance, and get ready to go. You might also want to practice while listening to loud music, while watching TV, or in an area where people are loud or might want to bug you. It will not be silent when you get on the blocks and you need to prepare for that!