EK I will second exactly what Mersey has said, and no matter how much prep you do for it, you somehow never feel ready. No matter how many times you go over the mock, like Mersey said, you are being sent for it because your instructors think you are ready. You won't do anything in the test that you haven't already done in the training (well, that's not quite true for me!).
Best of luck and let us know how you get on,
Lee
Edit: Guys, looks like were posting at the same time - I really do appreciate those kind words, they mean a lot....