You won’t keep most of what you memorized for tests. You’ll keep how you learned to deal with hard things.

Most specific content fades, and fairly fast. What stays is procedural: how you handle a deadline, what you do when a page makes no sense, whether you ask for help early or at midnight, how you recover from a result you did not want. School runs two syllabuses at once and examines only one of them. The unexamined one is the part you keep.

For your next exam, pay attention to your method as well as the material. Notice what actually worked and write it down. That note outlasts the content.