Breakthroughs (or successes) don't often come from just one thing. Instead they are a culmination of many small changes added up. Instead of looking for one big thing that you can do to change your results, focus on small 1% gains. For example if you want to learn a new skill, aiming to do huge amounts of time per day may be less effective than doing a more manageable 10 minutes over a long period of time.
To make change consider what small actions you can take. You could try reading your notes for a few minutes before each class, doing a short amount of research so that you have some questions to ask your teacher, or doing a short amount of exercise each morning. Each of these has a marginal effect on your total grades, but when added together with other small changes their impact can be huge.
Source – Clear, J. (2018) Atomic Habits. United Kingdom: Penguin Random House Business Books. (See pages 1-28)