It's great that you are looking at this now for a 2016 HSC. One thing that I have seen more and more in the years - students that struggle with the strength they need to get through a decent sized essay.
My best bit of advice for you would be to write whenever the opportunity presents itself...
As a teacher I would advise you approach this one of two ways (and both of the above posts have made very sound and valid points):
1) Your love of English is a great start, but you must be able to compose a piece of work that would hold up against the marking rubric. If you aren't confident...