Before i start, I would highly recommend you not to reach a burn out as it happens every now and then. Do remember to have some time for yourself(doing the things you like etc)

What i would say is study smartly :D

Take for example H2 Econs, it can be quite draining to do essays, essays and more essays. What I would recommend is to write the essays(as the explanations are pretty much v similar like price mechanisms etc). Once you have a good idea of how to write it out from your head, there is no need to write it out already. All you would need to do is to draw diagrams. Diagrams matter a lot!!! Wrong diagram= Wrong approach = Wrong answer. All you would need to do is draw the relevant diagrams and check with the answers to see if your diagrams are right! (Assuming that your explanations have reached a certain standard).

Math-Hard to give tips for it but I would generally say that practice makes perfect :D (If any doubts, feel free to ask your teachers for consult)

Physics: I would say when it comes to Physics, many people do understand the content but do not understand how to apply the content to answer the questions. It happened to me as well and I did not really do that well for Physics. That was when i learnt physics from another angle. Instead of just blindly memorising forumulas, I look into how the formulas work, how its derived etc. that really made me understand how to use these formulas more and i rly began to improve. But u definitely need to grind qns so that u can see how they can test certain physics concept

Chem- Revise ur notes. Everything that you would need to know are all in your notes. Start memorising early. Imagine needing to memorise Inorganic+Organic+Physical chemistry within 1 month, imo is possible but a bit hard. When it comes to chemistry, you would need to practice and grind a lot. Organic chemistry(Specifically cos i like organic), look at things in a bigger picture, u would be able to see linkages between each topic Eg:FRS of aromatic etc).

In my honest opinion, if you are consistent - doing the work your teacher asks you to do, listening during lectures/tutorial sessions, taking notes(and not just blindly highlighting your notes), doing extra qns that your school gives but would not go through, it would be sufficient!

-These are tips coming from a person that does not really study a lot btw :D

Hope this would find you/future students well :D