if you go in with this...mindset in year 12, you'll end up getting far too stressed and it will be detrimental to your entire score in the end (trust me, i stressed like an insane person because of a lot of things during mid-years and ended up not being able to work that well), since then i've relaxed and realized your ATAR/year 12 is not everything.
sooner you can realize how little your ATAR means in the long run as there are about 5million other pathways even if things don't work out; the better off you'll be and the better you'll probably perform.
not saying relax and don't work, but if something doesn't go your way don't stress about it and try to just enjoy your year. year 12 teachers treat students at a more equal level and the social life is great, enjoy lifeeeeee.