You could make a mistake that completely turns you off. It's still feasible for you to pass with a few minor errors because the examiner is forgiving. If you make a mistake on the driving test, put it out of your mind for the time being, get over it, consider what comes next, and pay attention to your driving. There's no use focusing on errors, and you shouldn't feel defeated or give up during the exam. Because what you may perceive as a significant error may only be a minor driving error to the examiner. Keep your calmness and have faith in yourself!