Your teacher hands you the first bad grade of the year. Here is what you do:
Grab a stack of flashcards and pull out your exam. You are going to look at every single question you got wrong and write it down on a flashcard. Then on the back you are going to write the answer along with an explanation.
You will start doing this for every exam and keep all your cards safe in a pile. Then, a few days before your finals, you are going divind them into subjects, shuffle them and answer them.