Wins tell you what worked. Losses tell you why. You need both, but the second one teaches faster.

Winning confirms that something worked without telling you which part. Losing is specific. It points straight at the thing that broke, and it will not let you look away. That is why a hard loss can move you further in a week than a comfortable win moves you in a month, though neither helps if you never go back and look.

After the next game or test that goes badly, give it ten minutes before you put it away. Write down the one thing that actually went wrong, not a general verdict on yourself. Then take that one thing to practice.