Make the mistake impossible

Many cooking hobs now have a small sensor beside each burner. If the flame goes out, the gas stops. Nobody has to remember anything.

The same hob will happily let you leave a plastic chopping board on the burner next to the lit one. The guard covers one danger, not every danger. That is fine. A guard is not wisdom. It is a single, narrow refusal built into the thing itself.

Plugs that only fit one way round. A phone tray that will not close if the card sits upside down. Medicine bottles a small child cannot open. In each case someone looked at a mistake that kept happening and stopped trying to educate people out of it. Changing the object was cheaper than changing everyone.

The useful part is that you can build these for yourself. A small online seller who reads the address back to the customer before calling the courier. A shopkeeper who keeps the cash drawer key on a cord around his wrist. A writer who sends the draft to one friend before it goes to anyone who matters. A student who sets two alarms on opposite sides of the room on exam day.

None of these depend on being careful on the day. They assume you will be tired, rushed or distracted, because sooner or later you will be.

Look for the place in your own work where you hold your breath. The order that goes out wrong, the message sent to the wrong group, the price typed with a zero missing. That small held breath is a signal. It is telling you exactly where a guard belongs.