The best advice I could give someone doing their HSC is not to freak out. At the end of the day, you did the best of your ability and you can be proud of that. Do the best you can to make sure you're happy with yourself. Rely on your friends. Work together - you're always going to work better together so keep those friendships up and share your notes. Don't stress about what you're going to be doing immediately after school, I mean you've got like heaps of time. It may seem like the biggest thing in your life. It's just a stepping stone that will help you get to where you want to be.