Counting down...
The best advice I can give is to trust in yourself. You have done the training.
I used to get knots in my stomach before every race until I realized I was doing this for fun. During training I used to always try to figure out how quick I should be able to finish the race, this usually stressed me out so I changed my gameplan to just go out and have fun and enjoy the day. Not all of the knots, but most of them went away.
I'll second D's advice. Just have confidence in your training and remember to have fun.
There's a few Sports Psychology articles in the training section. Some good tips in there for preparing mentally for the race.
http://www.trifuel.com/triathlon/sports-psychology/index.php
Much of the nerves (at least for me) is not knowing whether I've forgotten something or am unfamiliar with the course, stuff like that. So if you practice a couple transitions at home and prepare a list of stuff you need to bring with you (some ideas for stuff: http://www.trifuel.com/triathlon/gear/pre-race-gear-check-000244.php) you be more confident and comfortable going into the race. If possible I'll also ride and run the course a couple weeks prior, or at least drive it the day before just so I know what it looks like. That usually helps as well.
But remember, just have fun and 90% of the other participants are just as nervous as you.



Alright I've trained all winter. The bike is tuned and lubed. I'm ready. I know that. So why do I still have this knot in the stomach feeling?
I'm racing my first race, a duathlon here in Delaware, on Saturday and despite all the preparation, I'm still haveing those doubts that I'm sure alot of others have gone through.
Any adivce?