What does it mean that feedback from errors is the most valuable feedback?

Errors teach you more about your systems than successes do.

Example: You launch a new weekly planning ritual. For the first month, three of your four weeks go smoothly — tasks complete on time, energy stays manageable. But one week collapses: you overcommit on Wednesday, skip Thursday's deep work block entirely, and finish Friday with a backlog larger than where you started. Most people focus on the three good weeks as validation that the system works. The single failed week contains more information. It reveals your system has no mechanism for handling unexpected load, no rule for when to decline new commitments mid-week, and no recovery protocol when a single day derails. The three successful weeks told you the system works under normal conditions. The failed week told you exactly where the system breaks — and those breakpoints are the precise locations where improvement is possible.

Try this: Identify one error or failure from the past two weeks — a missed deadline, a conversation that went poorly, a habit you dropped, a decision that produced a worse outcome than expected. Spend fifteen minutes writing answers to three questions: (1) What specifically went wrong — not the emotion, but the mechanism? (2) What assumption in your system does this error reveal was incorrect? (3) What single adjustment would prevent this specific failure mode from recurring? You are not journaling about feelings. You are performing root cause analysis on your own cognitive infrastructure. The adjustment you identify is worth more than ten successful repetitions of the same routine.