An error log turns a wrong answer into a specific learning task. The goal is to identify a repeatable cause, not to label yourself as careless or weak at a subject. Different mistakes need different responses. Record the question, your original reasoning, the correct reasoning, and the earliest point where they differ. Classify the cause: missing knowledge, misunderstood wording, calculation error, or an unchecked assumption. Write a correction you can actually use next time. If you repeatedly confuse area and perimeter, draw both on the same rectangle and label their units. If you skip a condition in a question, underline conditions before starting. Reattempt the problem later without reading your correction first. Try it today: Add one recent mistake to a four-column log. Create a new question that tests the same weakness and explain how you will check your answer.