First of all you should know marks really do not not reflect your real value. You can lead a very successful life despite getting low grades.

So after whatever marks you get in 12th CBSE boards you should really ask yourself what is the subject you are most interested in. There are many students who take science, commerce, humanities in 12th and then change subjects in under-graduation realizing they shave different field of interest.

So you should also analyse what you like and no matter in which course you enroll in, be dedicated to it from 1st day.