As a recent grad, I completely resonate with the feeling of burn-out, especially in senior years. I found that, personally, I needed to realise where my limits were and try not to overly exceed them, because the mental struggle with making your way out of burnout is so much worse. After trials, I was severely burned out, and honestly, I was lucky enough to be able to bounce back quick enough before HSC but you can imagine after HSC it was even worse. It's been like 3 months since HSC and I'm finally back into productivity after giving myself a long-deserved break from that HSC grind and burnout LMAO.
Another cool tip that I could suggest is, I found that there was no point in studying till the very, very last second of an exam. It reaches a point where you know your exam techniques and content well enough before the exam, so, the day before the exam you should try to just rest yourself and prepare mentally. The mental game of exam prep is something that isn't talked about enough so you should also allocate a bit of your pre-exam prep to hyping yourself up and making yourself mentally fit.