I stalled the car early on in my test. Thinking that was it and I'd failed, I just fired it up again, set off and got on with the rest of the test, not bothering whether I did it right or wrong - and I passed.
My instructor said I probably passed because the examiner saw a calm, confident driver who wasn't panicked by a minor problem such as a stall - something that happens to every driver at some point. Passing is as much about how you put things right as what you do wrong in the first place.
So, as much as you can, try to forget the examiner is there and try to concentrate on the road rather than him or her. Easy to say in hindsight, I know, but it's what worked for me, even though I didn't realise what I was doing at the time.