Honestly the year 12 exams are not the end of the world. Unlike what some unhelpful people have claimed on this thread, they are important, and it is good that you are motivated and want to do well on them - you're already in a better place than 90% of other students just based on that. But don't worry if you feel your results don't best represent your ability, that's what the mocks are there for. Consider them less as UCAS-deciders, but more as a progress test that makes sure you know how to revise well for the future. Don't worry, everyone does 'badly' on year 12 exams, and ignore the Amarjit guy.