My advice was tailored to some worries costargh had... I hope you can still make sense of it

Do you have any specific questions? You seem a lil panicky and stressed. *hugs* Perhaps if you figure out exactly what's worrying you we can help you target the problem and calm those concerns.
If this is your first year 12 exam, perhaps you would like advice regarding exams in general, and some strategies to deal with worst-case scenarios?
It seems to me that your worst-case scenario may be that you get in there and 'freeze' in the way you did for your SACs. This is where I think reading time comes in handy. Read the whole exam, and find a couple of 'quick marks' that you can do easily. Do those questions first to get your confidence up, fend off the nerves, and get the ball rolling. Everyone's always nervous before they start an exam, and usually into the first few minutes of writing time. After this though, the knowledge takes over and you forget the nerves. Remember... you don't have to start your exam by doing Q1a... if you don't understand the first question, then start with another one and don't sit there worrying about something only worth a couple of marks - move on, but keep it in the back of your mind ...sometimes you'll figure it out or even end up reading something in the exam that makes you remember what the answer is.
Perhaps you need a few in-exam stress-countering techniques as well, in case you find yourself overwhelmed during the exam? Just let us know what you need, and we'll be happy to help ^_^