yeh, I agree with whats been written. I would only add this - if you think you have made a hash of something, then 'throw it away' and get on to the next thing. Don't let it niggle you and upset things, just forget it. One thing I was told was that if I did something real cr&p, then consider saying to the examiner 'I'm sorry,but I can do that much better - would you like me to do it again?' chances are he will just let it go.
Remember, he wants to see that you are safe, not some mega-qualified test pilot. Try to relax and enjoy it and good luck - let us all know how you got on
kind regards
TSM