Don't give up! Work as hard as you can - if you put the effort in and know that you tried your best you have no reason to feel embarrassed about the result
Well, if someone tells themselves they will not fail, and endeavours, assuming that their reasoning is that they know nothing on the exam, to learn as much as possible in what time they have left, they will probably not fail (unless of the course it is like an hour before the exam..) It's about confidence and motivation, which are not there when one thinks "I will fail this exam"
Honestly, just kill me now so that I can save my embarrassment.
Ah, if it was the Tudors then I may have been able to help. Remember, you've got the AS behind you, as well as coursework (if you do Edexcel), and that's a massive 70% of your grade. Trust me, you can do this!