The first thing is the Driving Examiners (DE) are just making sure that you can drive safely and be a safe driver, for life. The DE is not out to fail you to meet a quota, or because it is Tuesday and we don't pass people on Tuesdays. The DE wants you to pass and get your licence. In fact, at the start of the test, you already have your licence and you just have to demonstrate to them that you can drive safely.
Here are some common error that learners trip up on during their test.