Dear Aspirant,

It depends on the possibility of that particular part to come in exam .Suppose you have left that part which has a higher weightage ,then it will be a loss for you. Your overall rank will go down. But if your exam is very near then you must not revise new topics.

It will cause problems. So only make strong your old topics and revise them many times. But if you have left the part that has a very low weightage in JEE exam then it has no loss for you. But now you can make your other topics strong.

So don't fear at all , be confident and focus on your studies.

Hope this helps.