Time is the villain. No matter how hard you study and how good your basics are, if you can’t manage your time, everything’s going down the gutter. D
Hence, don’t waste too much time on a question or a topic you can’t understand/solve. It is better to ask them from your teachers.
At my days, approach of most of students was like: I’ll solve the question even if it takes 12 hours to do it! I also did it many a times. Many of your teachers will also tell you to do
it. That’s stupid thing to do. You can’t solve a question when you don’t know the tactics of
it. Learn tactics first. Develop a proper approach. See videos online. Don’t waste too much time.
Similarly in exam, skip a question if you are unable to solve it and get back to another question without wasting time. Manage time properly. Solve mock test papers and time yourself as you do them. Keep the time limit stringent and be honest with yourself. Regular practice of time management by solving practice papers will highly reduce your chances of not being able to complete the paper in the exam or making silly errors.