I was convinced I was going to fail my test on the way to the test centre I stalled twice at a roundabout and got peeped at for cutting in front of someone. But when you get into the car for your test you just seem to focus and, for me anyway, I didn't feel nervous anymore. My examiner was so nice and I made loads of small mistakes out on the road but I passed with only one minor. The driving examiner is not there to pick up on every mistake you make, just the ones which could be dangerous
You could just be having a bad day driving don't let it get you down, I'm sure you'll do great!!