It depends on your personality. It doesn't help me at all to get all intense and serious. But you must have a plan for your race, know that your gear is set, know how long until you race, and once you have that stuff set, you can relax and have fun. When it's time to go, I just get up and do it, without thinking about it much. It's really easy to over-think and be self-defeating. I see this a lot, and have definitely done it from time to time. Just be cool and have fun. It's for fun, right?