asap.. How hard did you study this year? did you see the change when you put your head down in your actual results? The thing is.. i actually have never studied before .. (well not excessively)
Mate. If you want to achieve, you do actually have to buckle down and study (like real study - on a desk, without a screen in front of you). Anybody who brags that they don't study for VCE (you know the ones - that always achieve the highest results), are lying 95% of the time.
My philosophy was based on my brother's. He also worked his butt off during the holidays (basically zero relaxing) and was able to ease off a little during the year while everyone else started studying. He achieved an ENTER of 99.75. Given this method has proven results, I also did the same.
Not studying before CAN be detrimental, but doesn't have to be. The choice ultimately lies with you. If you're willing to sacrifice your social life (During the year I went out a total of 2 times; including my 18th which consisted of merely going to the movies), you will amaze yourself with the results that you begin achieving.
VCE is not the most important thing in the world. I totally agree with everyone who says that you need to relax and rest to avoid burnout. But try for yourself and study non-stop for a while and see if you are actually "burnt out".
Sorry for my long posts

P.S. +1 for Chavi's post. You have got to be self-motivated. Find something to spur you on. My motivation was a list of things I would buy if I achieved a certain result.