Well then you are toast!
Just kidding. I'm assuming you must have your 50 hours of behind the wheel time with your parents or other adults, otherwise you wouldn't be ready.
Remember a couple of things.
First, it isn't the end of the world if you don't pass. Lots of people fail the test on the first go around so don't psych yourself out by thinking you absolutely have to pass. Relax.
Second, remember what you were taught and be very deliberate in what you do. When you get in the car, put on your seat belt, adjust your mirrors and ask the DMV tester to put on his/her seat belt.
Third, as you drive during the test, perform as if you are showing your dad or mom how well prepared you are for the test. If you drove well enough to convince them, then you can pass the test as they were probably harder on you then the DMV guy will be.
Fourth, take the easy car if you have a choice. If your choice of vehicles is a Suburban or a Prius, take the Prius.
Fifth, don't hit anyone or anything.