Oh how come?
I thought the HSC was important as it would help you determine your future into getting into uni
Sure the HSC is important, but its only as important as you make it out to be. If you truly have your heart set on a specific career path/degree it shouldn't matter if it takes you another few months to get where you want to be. As you said, your ATAR gets you
admitted into a university, it has no further purpose after that. As soon as you accept an offer it literally doesn't matter anymore.
Personally I haven't done any extra study (just normal homework) for the past 1-2 weeks, because I decided a long time ago that the HSC wasn't something that I wanted to fully define my last year at school. So I've been making the most of every single class party and free period and after school shenanigans to have as much fun as possible as I lead up to graduation, because I know that they'll be the times that I'll remember.
Not all the hours spent sitting at my desk doing practise papers.