If someone keeps misusing your trust, you’re allowed to ask for the key back.

Trust is something you extend, not something you owe forever. When it keeps getting spent badly, reducing what you hand over is the honest response, and it is not a punishment. You are matching the access to the track record, which is what you would do with anything else you cared about.

This can be done quietly. Share less, check before passing something on, stop taking the big news to the person who leaks it. If you want to say it out loud, one plain sentence about what happened and what you are changing will do.