I studied a lot...I was motivated because I did cosmology this year, and receiving the course pack at the end of december really made me wake up to the fact that there was a hell of a lot to be done, probably because there it was, all 1000 pages of it, sitting in front of me.
I've never found making myself study difficult because I tend not to study in a monotonous way...my advice would be to use your holidays, while everything is still new and fresh, to get to know your courses and familiarise yourself with the content...I think that too much of the HSC is trying to tick off dot points and coming up with 'what the examiners want' close to the exams, rather than enjoying the subjects you chose for their content.
So, try to do that these holidays, if you can.