Make sure you get enough rest the night before.
I know you can be anxious - the big day's tomorrow, I so darn want that ticket, etc. etc. all leading up to a restless night.
This lack of sleep, and the nerves of the test wear you out - I had them and I already held a ticket (from another country) when I did my FAA test. For some it's just the fear of taking a test.
I know of a guy recently in my neck of the woods who barely got 3hrs sleep the night before his ppl(h) check-ride; needless to say it affected his performance.