I used to be too trusting in some cases. Then I realized that and moved the boundary for what's trustworthy. Create standards people have to live up to before I trust them. If the standards aren't tight enough, move the standards. Maybe mine are too tight, but at least I feel safe. Maybe you can try that. It is possible to get some control. Realize that betrayal is about them more than about you. And go slow, trust little bits at a time so there isn't a neverending river of hurt as a result, just raindrops.