“Not my job” is true more often than it’s helpful.

The sentence is usually accurate, which is what makes it tempting. Accuracy is not the same as usefulness, though, and a shift or a team runs on the small things nobody’s description covers. Saying it draws a line and tells everyone where your help stops. Sometimes that line needs to exist, and the skill is knowing when.

Watch for the next time the words come to mind, then ask what doing the thing would cost: two minutes, or a real chunk of your evening. If it is two minutes, do it. If the cost is real, say what you can do instead, which lands differently from a refusal.