It's been posted so many times before but I still think it's worthwhile knowing: the train of thought the examiners usually have is "would I want to allow this pilot to fly my children" so safety and the ability to handle the plane is paramount - if you make a mistake, DON'T dwell on it, correct it, FLY the plane.
When I did my PFL, I totally forgot about taking wind direction into my calculations so came in way too fast for the field I had selected but instead of getting into a mess, just said "oops, am too high and fast, I'll go for that one over there instead" - at the end of the day, he's not expecting perfection, the learning curve of a pilot continues AFTER you pass your skills test and you start to expand your horizons, the examiner just wants to see that you are in control of the plane......
As for Nav, use all aids you have at your disposal to confirm to yourself you are where you believe you are - VRPs, VOR etc. Your preparation for the flight will help you too.......