How do I carry the weight of catching errors no one else sees?

You are the one who catches the error before a wrong result goes out, and you carry the weight of what that would have cost, though no one else ever sees it. That is a lonely responsibility. When you succeed, the near-disaster simply vanishes, and only you know how close it came and what your attention prevented. Let yourself hold both truths. The weight is real, because the stakes are real, and feeling it is part of why you are good. But carrying it silently, with no one to witness the saves, can slowly wear you thin. The consequences you prevent are invisible to others; they do not have to be invisible to you, and they do not have to be borne entirely alone. Keep some quiet record of the catches that mattered, and when one weighs on you, tell a trusted colleague what you caught and what it would have meant. Let the save be seen by at least one person. You protect people who will never know your name. Make sure someone knows the weight you carry to do it.