With procrastination, you will procrastinate no matter what - it is a part of human behaviour. The key with procrastination is to manage it so that it doesnt become harmful. In order to do this, focus on the setting up your work in such a way that it encourages you to work harder. As mirakon has said before, the HSC is all about attitude. Break the work down into small achievable goals. If you achieve these small goals you will feel much more confident with work and this will increase your morale and motivation. Remember, the best way to defeat an enemy is to cut off their strategy - the worst way is to take them on head-on. Procrastination's strategy is like a snowball, the more you put off doing the work, the larger your workload becomes, thereby further crippling your desire to do the work. To beat it, you attack it's strategy and prevent the snowball from getting bigger by chipping away at the work.
There is an old saying which goes "it's easy to commit to an idea, but it's hard to commit to a process". To commit to the process of doing well, you need to focus on the work itself - having long term ATAR goals is all well and good, but they often fail to motivate people in the day to day process of studying.
I know it seems like I am talking shit, but I actually used this strategy and I found it to be highly effective.
