I am sure u are not the only one who is worried about not being able to crack the exam. We all have gone through this thought process not once or twice but everytime you attempt a competitive exam this thought will cross your mind.
Coming to your question, then if you really feel that you want to clear the JEE exam then i would say go for it ,take a drop and prepare and you will succeed…also my personal suggestion would be that u should take a drop ,this is what everyone deserves to show their potential, a second chance