A test covered in red ink is a treasure map. It shows exactly where to dig.

Marked mistakes are the most specific information you will ever get about your own understanding. A clean paper tells you only that you knew what was asked. A marked-up one tells you where the gap sits, how wide it is, and whether it is carelessness or something you genuinely have not learned yet.

Rather than filing the paper away, spend twenty minutes sorting the errors into two piles: things you knew but rushed, and things you did not know. The first pile is a pacing problem. The second is a study list, and it is usually shorter than you fear.