Failure is expensive enough; do not waste the lesson too.

Failure already charges you in time, money, standing, and morale. Not extracting the lesson means paying that price and receiving nothing, which is the one genuinely avoidable part of the loss. The cost is sunk; the learning is the only recoverable piece.

When you are past the worst of it, spend an hour deliberately on what you would do differently and what you would keep. Write it down where you will encounter it again. That hour is how you get something back for what it cost you.