The face you bring into a room includes more of the day than anyone there can know.

People read your expression as a response to them, because that is all the information they have. What it actually contains is a phone call from the morning, a bad night, an ache, or a piece of news you have not told anyone. Almost every misreading between people starts here, in the assumption that a face is about the present room.

When someone seems short with you, allow for a day you know nothing about before deciding what it meant. It is also worth saying a plain word about your own state when you arrive somewhere carrying something, since one sentence saves everyone a lot of guessing.