Some people keep your secrets the way a pawn shop keeps your watch: until they want something for it.

Something given in confidence can be held, or it can be stored. The difference only becomes visible under pressure, when what you told someone is suddenly worth something to them, as something to hold over you, or as currency in a conversation with somebody else. Most people do not plan this; they simply discover a use for it.

Before you tell someone something costly, ask whether you have seen them hold anything before. Look at what they have told you about other people, which is the clearest preview available. Give in stages, since a small confidence is a cheap and accurate test.