Hello,

Firsly, it is a very rare instance when someone is happily interested in science and wants to pursue it. As you said, you have scored good marks previously, so I am assuming you have base concepts intact with yourself. If that is the case, you dont need to do much.

Just keep the things regular. It shouldn't be that after today, next time you practice maths its been weeks. Just keep in mind that, with regularity and punctuality, 80% is easy. Since you are not preparing for JEE or NEET, thus you can afford a longer approach for the study. Try to clear your concepts, if any doubt, have it solved as soon as possible, fight with it.

Dont keep backlogs, personally speaking, I missed coordinate system of XII maths, and I regret it very much as I couldnt complete it even till the last.

Hope with these little things in mind, and clarity of concepts, you would all the tests and exams you face.