Hi, don't panic until you get the actual results. Move on. If you think you've done badly (which you probably haven't, we all have a tendency to assume the worst after exams) then take this as a lesson to revise more effectively and ensure you understand everything. If you revised really hard for that subject, maybe your exam technique let you down? If so, just keep practicing and definitely ask your teacher for help.
Lastly, try not to worry! I'm doing as level at the moment so I can't offer insight into how important a2 mocks are, but I do know that worrying is so futile and distracts you from improving- plus, most of the time you'll end up surprising yourself and getting good grades!