BREATHE!!! Seriously, keep your mind on your breathing and let the muscle memory do it's thing. If you find yourself holding your breath and clinching and bearing down RELAX AND BREATHE or you'll gas right out. You're going to have enough adrenaline pumping through you that you'll burn out fast if you don't just relax and breathe. Keep your ears open and listen to your coaches, breathe, listen well, breathe, don't panic, breathe, listen well. Do that and you'll be fine. It's not like you're going to learn any new techniques right there in the middle of a match, right? So why worry about the techniques? You know what you know and your coaches will point out opportunities for you and guide you. All you have to worry about is not gassing out so you can do the things you need to. So just breathe.
Don't neglect the mental preparation. Visualize yourself being there on the mats and winning. Be specific; work through positions, transitions, and submissions all the way from beginning to end. Do you see yourself pulling guard or shooting for a takedown? If you shoot for the takedown, what kind? What position do you land in after the takedown? Where do you go from here? See the fight playing out hundreds of different ways with you winning every time. See it from beginning to end and don't take your focus off until you see your hand being raised. Coach Herzog is big on the total-person concept of preparation. Use the search feature to find his articles on preparation; they're full of good stuff.