If you got it wrong and know why, you’re ahead of everyone who got it right by accident.

A wrong answer you understand is a repaired piece of knowledge. A right answer you cannot explain is luck, and it will not be there next time, with the added problem that it feels like competence. Marks treat the two as identical, which is why they are a poor guide to who is ready for what comes next. Knowing the reason is the part that travels.

After your next test, go through the answers you got right and tick only the ones you could explain to somebody else. Put the rest on your study list beside the wrong ones.