Be thankful for the people who knock, literally and otherwise.

A knock is a small act carrying a large assumption: that you have an inside, and that it is yours to open. The same thing turns up as asking before borrowing, checking before posting a photo of you, or asking whether now is a good time rather than launching straight in. It is easy to miss, because the people who do it never make a show of it.

Think of one person in your life like that and tell them, specifically rather than generally. Name the thing they do. Quietly considerate people almost never hear about it, and it is a short message to send.