The person cleaning glass restores a view that had been fading too gradually to notice.

Work that reverses a slow decline is almost impossible to appreciate, because nobody registered the decline. The cleaner gets no thanks for the returned brightness, since the room never felt dark, only slightly less good in a way nobody could name. A whole category of labour is like this: maintenance that is only visible in its absence, and invisible when it is done well.

Thank someone this week for something that did not go wrong. Say what you noticed, even if the noticing came late. People doing restorative work rarely get told, and being told once tends to be remembered for a long time.