GAME PLAN:  true, this isn't football, but when you are at a meet, you SHOULD have a plan of action for EACH swim. Break the race into parts : start, first lap, turn, finish.  Pick ONE specific skill to focus on for each part. THINK: "stretch", "strong kick", "tuck chin", "hard to the wall".  Then keep that focal point in your mind as you swim each part. 

This can help you stay relaxed and swim "your race".