Just relax, as long as you worked your ass off and know that you can't have done any better revision, you will feel proud regardless. And if you do get grades you ain't happy with, you have a last chance to push yourself for a level revision, learn from what mistakes you made at GCSE revision and fix them for a level. We literally do learn from our mistakes. It will be the end of the world if you mess up a level and plan to go to a uni but it won't be end of the world if you don't get good grades at GCSE cos you have another chance. And if your scared what your parents think, just think if your happy, then all is good.