Hand out trust like a learner’s permit: a little at first, more as they prove they can handle it.

Trust works best in increments. All of it at once means one bad judgement can cost you everything you handed over, and none of it ever means nobody can get close. The middle version is a graduated system: small things first, then slightly larger, with the next level earned by the previous one going fine. That is not coldness; it is how you would lend out anything valuable.

Work out what the small version of a test is with somebody new. One secret that would not ruin you, one promise that would be inconvenient to keep. Then watch what happens and decide the next level from evidence rather than hope.