All you need to do now is to keep on taking full sample tests (e.g: do one complete test a day) in actual conditions and timing (including breaks) to get your rhythm for the actual DAT. Once you get through several of them you will feel less nervous about taking the actual one. But leave the day before the actual test to relax!
make sure you get a good amount of sleep the day before!! dont' sleep too long but just enough...it's actually a really important factor in my eyes. like everyone else said...just take practice exams each day and relax the day before the exam. good luck and try your best!