What is "metacognition," and why does it decide how well you study?

Metacognition is "thinking about thinking" — monitoring and regulating your own learning as it happens.

It has two parts: monitoring (noticing what you do and don't know) and regulation (changing what you do next — more practice here, move on there). Almost every study decision you make is downstream of a metacognitive judgment: what to review, what to skip, when to stop.

That's why accurate self-assessment matters more than it sounds. If your sense of "I've got this" is wrong, you'll pour time into the wrong material and abandon exactly the things you haven't actually learned. Good technique is wasted if it's aimed by a broken gauge.