Hey there! Apologies for the forthcoming essay

What sweetcheeks said is awesome.
I'll address the night owl thing first - I can definitely sympathise, I'm most productive at night, and I found that instead of having my relaxing time at night after doing homework, I'd do it when I got home from school. You just have to sort out a schedule that suits yourself (making a study timetable could help, where you block out the times you can't do study and just work around it - personally this stuff never helped me but I know that it was super helpful for some of my friends!). In terms of trying to be more productive during the day - I found setting myself goals was helpful (eg: doing 20-25 minutes of study for a particular task or subject then having a break for 5-15 mins afterwards), even if I had to set my timer so I would study for the set time...then once you've done it, you feel good about yourself (ngl, I did reward myself with snacks), and if you keep on doing it you get into a routine! It's just a matter of perseverance and determination.
Perhaps my favourite bit of advice is to use your class time at school wisely - I cut down how much I had to study so much just by paying attention in class (you'll be surprised how many people don't do this) and engaging with my teacher and asking them questions.
I personally found that if things got overwhelming for me (lots of SACs during a week, or emotions running high for whatever reason, etc.), I just had to take things one day at a time and not think about how many SACs I had in the coming weeks (this makes you even more overwhelmed). You just have to keep on going and take each day as it comes (another bit of advice thrown in here: after SACs and exams, don't dwell on mistakes you think you made or things you should have done, because it doesn't help anyone and is just a way to make yourself upset easily)

I had a lot of personal troubles in year 12 to deal with, so this was how I survived a lot of the time, and it worked so well - you get into a pattern and it becomes so much easier to get by.
Another important thing is
don't expect that you have to study every day. Make sure you give yourself breaks. The world won't end if you miss a night or two of study. I think breaks like this are also important for mental health - otherwise you might burn out.
This kind of moves nicely into my next point: don't neglect your health and your social life during year 12! Save recess and lunch for catching up with friends, go to parties or whatever it is you like to do, and maintain your friendships during the year - they're so important. Having supportive friendships is so important, because you can help each other get through the good and bad times in the year. And if you are struggling, go see a trusted teacher, school counsellor, your GP, etc - don't just try to ignore the problem, because bottling it up will be the opposite of beneficial.
I think also something that is so important is to know that year 12 isn't the be all and end all - yes, it is important, but if you don't get the ATAR you want, or you don't get into the course you want, there is always another way into things! (You definitely have the right to be disappointed though, I'll just put that out there). However, with me mentioning ATARs, don't let your ambitions for your ATAR consume you - don't let it get in the way of friendships, and don't use it as your sole motivator throughout the year, because I honestly think that will just lead to burn out (but honestly, it's horses for courses - I'm sure there are people out there who get through the year just fine being motivated by the ATAR

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Last but not least, enjoy the year!! I can honestly say it was the best year of high school for me...get to know your teachers (this makes life so much easier), talk to different people in your year level, and try new stuff!
tl;dr: take it one day at a time, don't be afraid to talk to people and get help, believe in yourself, work out a system that works best for you!All the best for the coming year, and feel free to PM me if you want someone to talk to about anything!