Don't think about a pink elephant. Now we're both thinking about pink elephants. That is how our brains work. They do not process the "don't" in that directive. Ever wonder why so often it happens that you tell yourself not to do something and then find yourself explaining, "I don't know why I just did that! I kept telling myself not to." Our brains just hear the action, "think about a pink elephant." Watching children play soccer is a great place to see this in action. Often coaches and parents are yelling what not to do and the children often do exactly what they were told not to.
Acceptance. I accept that I am now thinking (and writing) about pink elephants when that is not at all what I want to be focusing on. But the more I fight the thoughts, the stronger they will become and the more I will continue to write about them. If I accept the thoughts and roll with it, they will eventually move along so I can focus on my desired point. If we acknowledge and accept what is happening (not performing as well in a competition as you had expected), you can then move forward in readjusting your plan to continue toward your goals rather than getting bogged down in the exasperation of things not going your way. Update your language to focus on what you want to do or what you want those you are coaching to do.