Hello

Firstly I would say that 'never stop trying' - practice as much as you can and stay focused on your target.
In whichever subject you are weak or you think you cannot score good.. then don't just leave it.. take a determination and run after the subject.. i.e read + understand + make notes + practice endless.. This way of studying will surely get you good marks + you'll gain interest in that subject. Hope you're getting my point.!

Take a particular chapter which you're finding tough + you know it's important.. read it once from NCERT and understand what the chapter is trying to say.. then note down the important points + formulae in a separate book. Practice maximum number of MCQs from that topic/chapter.. >> by doing this you'll know the question-level-pattern + the logic where and when to be applied and also the applications of the formulae..!

So prepare well and study smart.!
Hope this helps.!
Good Luck.!!