A little secret James, if your examiner is from another school very few fail. Why, because its a nice little earner and if you start failing people guess what?
Also consider that not even your examiner can fly a prefect test, we all make mistakes, its what you do when you make the mistakes that shows what sort of pilot you are.
The old advice of never dwell on a mistake is very valid, Dwelling on a mistake will spoil the rest of the test.
Many candidates fail to prepare properly, especially Notam's & weather, Mass and balance and fuel planning.
If you come over to the examiner as someone who has prepared meticulously he will be in a much better frame of mind when dealing with subsequent mistakes than if you have done the absolute minimum planning.
Lack of a passenger briefing is another example of poor preparation and non understanding of what the test is all about. Treating the examiner as the most important passenger you will ever carry helps too.
Most flying schools that Ive come across seem to teach pilots to fly either solo or with an instructor. Flying with a passenger who is nervous and has never flown in a light aircraft before isnt the same as flying solo or with your instructor
Failure to use an aerodrome chart for taxying again shows poor preparation but seems to be the norm with most schools, who seem to think a runway incursion is some sort of holiday.