You must be positive. Your instructor thinks you will pass the Skills Test and he undoubtedly has hundreds of hours of experience. As a professional musician myself (performer and teacher) I am used to dealing with both perfomance pressure and with entering pupils for exams. I don't enter pupils unless I think they'll pass and I've never had a failure. As far as dealing with the test, if something goes wrong don't dwell on it. If I am playing in a concert and play a wrong note I cannot think about it as I will inevitably make more mistakes. Your mind has to be on the job in hand.
I heard an interesting bit of wisdom the other day (on Coronation Street of all programs!) - 'To fail to plan is to plan to fail'. You have done all your preparation - you can go into tomorrow with complete confidence that you will pass this test.
Good luck, and let us all know how you got on.