1. Know were your fitness level is for that particular race and don't let success or failure of one particular race define who you are as an athlete.
2. Visualization. In my case I right a story of how I want the race to go. Work through your anxiety triggers before the race and how you will deal with them.
3. Don't worry about the outcome. Stay focus on the present and do the things that you know you can control.
4. Have fun.