It's also quite important to be happy in your own mind that you are going to make the odd mistake on the test - there's never been a perfect test yet, be it in a 152 or a747 sim. If you recognise an error, own up and see if you can put it right, this is airmanship and will set the examiner purring. Then put it behind you and get on with the next item. You can enjoy the debrief of the error after he's told you you've passed!