i relate to this so much omg. getting over a not-amazing mark can be so difficult when academic achievement has been hammered into your brain since day 1. i remember doing 3/4 psych last year and i got a pretty average grade. being in yr 11 and thinking my accelerated subject was literally life or death, i let that grade dictate my mood and honestly change my view on the subject all together. i was so fixated on that one mark that it genuinely impeded my ability to study for the subject, despite exams being fast approaching. there was continuous doubt that this grade would absolutely sabotage my final score, when at the end of the day, i did fine. looking back now, you sometimes think, 'damn, i really cried over a number on a piece of paper.'
admittedly, I've still had a few moments this year where I've let average grades get the best of me, and it's definitely normal to have those moments. in all honesty, it sucks to put a fair chunk of effort into an assessment and not have that acknowledged in the mark you receive back.
and i agree! i think the best thing to do is let this frustration fuel your future efforts. you know you are entirely capable; maybe just had an off-day, a question caught you by surprise, or you just mind-farted several times during the sac. so why not give the next task your best efforts to prove to yourself (and perhaps your teacher if you're feeling petty) that you've got what it takes. and hey, if it doesn't work out, just keep trying - progress isn't linear!
i think you've got a great mindset that will really help you get through year 12! best of luck for the rest of your VCE journey!
-bw