As other have said, they are looking for reasons to pass rather than fail. My examiner said afterwards that his criteria was "Would I be happy letting my kids fly with this person?".
I TOTALLY effed up my navigation at one point, became totally flustered and annoyed as nav had never been a problem before (I assumed that a feature I could see was our turning point, even though we were nearly 10 minutes early, and became very confused when the rest of the world didn't fit the chart on my lap). Convinced I had failed, I decided just to enjoy the rest of the flight.
The rest of it went fine, general handling and circuits no problem, but I wouldn't have passed me based on the earlier mistake. So as we were taxying in I was rendered speechless when he said "Yeah, I'm happy to pass you on that".
Apparently the very thorough pre-flight with me talking him through what I was looking for also gave him confidence before we'd even got in the aircraft.
So my advice would be to just enjoy it, no matter what may go wrong. It's probably not as bad as you think, and if you weren't capable, you wouldn't be doing the test in the first place.