The person testing a limit and the person relying on it may never meet.

The person who sets a limit and the person whose life depends on it are often separated by years and continents. A tolerance is chosen in a design office, and someone stands on the result decades later with no way to assess it. Enormous trust is transferred between people who will never meet.

This is worth knowing on both sides. When you set a standard, write a specification, or make a decision that others will rely on, you are handing something to strangers who cannot check your work. And in ordinary life, notice how much of your day rests on the unseen conscientiousness of people you have no way to thank.