Second year uni student here. My best advice to you is to realise that for most subjects you already know the exam questions. You have a syllabus, live by it. Summarise the dot points. When it comes time to study for a specific exam, put your notes away and try to summarise the dot points being tested without the aid of a textbook or your notes.
I struggled a lot with finding the motivation to study during my HSC. I'd spend hours 'studying' but what I was really doing was doodling away on FB with a textbook open on my lap. Try to do at least a little bit of work every day. I found summarising the syllabus points really helpful because your progress was marked out on the paper- every time you complete a dot point you get to cross it out and that gives you that sense of direction and achievement. At the end of the day, if you want to do well you're going to have to study properly. Turn your TV/laptop/phone off. Sit at your desk with some paper, the syllabus and a textbook. The hardest part is starting- once you get into it you'll be surprised how much you can do!
Good luck and remember- the HSC is not as hard as your teachers/family/peers are making it out to be. Take a step back. You've got the questions, so chill out. Realise that you definitely have the potential to get whatever score you want, you just have to give a little.