Any advice on how to stay calm before a big race?

Take a few deep breaths, and remember it is a paddling race, and this is a fun sport. You can only control what's in your own hands, concentrate on your strengths and what works for you, and the rest should work itself out. It often helps to have a routine, and once you find something that you are comfortable with, stick with it, and it may make things go more smoothly. Be tough, and enjoy yourself!