A familiar face can contain changes that casual looking keeps overlooking.

Faces you see often are the ones you look at least. Your mind supplies the remembered version and skips the checking, which is efficient and means tiredness, pain or worry can sit plainly in front of you unnoticed. This is less carelessness than the way familiarity works. Recognition is fast and looking is slow.

Once this week, look properly at someone you see all the time, as though they had just arrived. Ask an ordinary question about how they have been lately and wait through the first answer. What you notice may be nothing, and the asking still counts.