FYI, cuz its not luck.
All HSC papers are double marked and all HSC markers undergo an intensive process of marking. They first determine a highly elaborate set of marking guidelines and then do some pilot marking on sample papers in order to determine that all teachers are on the same marking plane. These papers are pulled out of the papers done by students all around the state, so for some of you, you will have your paper marked by over 1000 teachers.
If these teachers do not allocate the same mark to the same paper, they go back to the marking guideline and then establish what went wrong - and do it again. Until it is done and patted down; everyone gives the same mark.
So pretty much, luck plays a VERY SMALL percentage of the mark you get. It is ultimately up to you.