Helpful Advice if you're Nervous.
Determining why you are nervous is a good starting point.
What real effect can my instructor have on the day?
Is there anything I can do on my own?
You only need to see the smile on a newly passed driver's face to know what it means to them, but it is not life and death. If you fail, you fail. The sun will still come up in the morning and go down at night. You can always take it again. No one will say "sorry, you failed. You can't take it again". A more philosophical approach will help calm you.