Most facts you study will fade by summer. The thinking they trained into you won’t.

A lot of the specific content does fade, and that is not a sign the time was wasted. The facts were the material your reasoning got built on. Working through a proof or an essay teaches your brain a way of moving, and that stays long after the dates and formulas are gone. You will notice it later, handling a problem nobody taught you.

At the end of a unit, ask what kind of thinking it asked of you rather than what it asked you to remember. Comparing sources, breaking a problem into steps, holding two ideas at once. Name it, because naming it makes it portable.