The cashier gave you too much change. That’s not luck. That’s a quiz with no teacher.

Nobody is marking the moment you look down and see an extra ten. There is no consequence coming either way, which is exactly what makes it tell you something. Choices with no witness are where your default settings get built, and those are the settings that run later when the amount is bigger and the room is full.

If it happens this week, hand it back before you have time to negotiate with yourself. The negotiation is the whole problem. A fast yes to the obvious thing keeps the obvious thing obvious, and that is most of what this is.