Remember the following;
Yes, easier said than done. But it is true. You stuff up one SAC, it doesn't matter redeem yourself on the next SAC, study harder for the exam to make up for it, study harder on another subject to make up for this subject.
Also keep in mind, there is still TAFE you can go to, and for those who don't like that idea, or are not suited for it, you can still go to University by transferring from TAFE>Uni, or from Uni>Uni. These days you have a LOT more options than your parents did. People only make out VCE to be "big" because it is the most direct pathway to University, and obviously your parents want you to do good.
Just please do not get into the habit of "oh dam I got an A instead of A+" =.=* grow up a little, save your energy.
It does wonders to your brain. Seriously try it. Your brain releases these chemicals which send "happy" signals or something, nooo it doesn't get you "high" haha, but it relaxes you. Just walk around the block, nobody is telling you to run and go gym or anything, just simple walking helps. It changes the scene, gets you away from a room with four walls.
Don't leave yourself till last, don't leave homework until the night before, study for SAcs well in advance (1 week should suffice), remember more shorter lessons or blocks of revision are more effective than fewer longer blocks of intense study.