The Forgetting Curve

German psychologist Hermann Ebbinghaus discovered something brutal in 1885: without reinforcement, you lose roughly 70% of new information within 24 hours.

The good news? Each time you review at the right moment, the curve flattens. After four or five well-timed reviews, information can stick for months or even years. The key is not studying more; it is studying at precisely the right time, right before you would have forgotten.