I disagree very strongly with the need to study 24/7 and not do anything else in life. From my experiences with everything, those with the very top marks weren't the ones who did nothing but study and I think this is because doing other things helps you focus more, clears your brain etc (plus it makes everything more fun). There's no real point in studying for 6 hours after school if your brain gets drained and you can't focus at all and don't absorb anything- you're just wasting your time.
When you study, study. Don't go on FB or split screen and watch a movie whilst you study. That way you'll finish early and you'll still have heaps of time to do fun stuff. If you just watch movie and study at the same time, first your study will take longer so you'll be less productive + it's not as fun as if you just finished everything and then had some 'guilt-free' time to do whatever the hell you want.
Also, its good to have an idea of where you want to go after school. If you are aiming for med or law, that obviously requires a different sort of effort and motivation to if you were going for arts. At the end of the day though, you can only do your best. Learn how you study best, do that (and stuff whatever anyone else says) and prepare for tests properly and whatever happens happens. Don't beat yourself up over mistakes or fails etc. Everyone does them. I was ranked 33rd after my first HSC physics assessment and I ended up with 96 in phys. I got 10/15 for a Frank essay and ended up ranking 3rd for the year. I've made retarded errors in everything but the point is, I didn't let it affect me. Its in the past- look at what you did wrong, find out how to fix it and then forget about it. You can't change your marks by stressing so move on.