What belongs in your CLAUDE.md because Claude got it wrong once?

A Reddit user asked what instructions people add to their CLAUDE.md file after Claude makes a mistake. The user noted the temptation to create a new rule for every annoying session, but questioned if every error warrants a permanent instruction, as some are task-specific or may become obsolete as projects evolve. They invited others to share a line from their CLAUDE.md with a story behind its inclusion.

This discussion uniquely focuses on the practical, user-driven evolution of AI instruction sets, unlike typical theoretical debates on prompt engineering.