Something that helped me with trust issues is to understand that you can never trust anyone 100% all of the time because you cannot control others or exterior situations. You’ll go out of your mind if you try BUT what you control your response. Rather than learning to trust, it’s learning to accept perhaps you can’t but finding what you will and won’t accept, how you respond to that and the betrayal should it occur. Trust yourself to leave situations that you’re not comfortable with, have strength to do that, have ground rules and implement them, not self sabotage through second guessing and paranoia, know you can’t change someone else only they are responsible for their behaviour, knowing what level of trust you’re happy with for different situations and so on. Judgment correct or not, if you’re happy at the time with your action as a result of their perceived behaviour then it doesn’t matter, the important part is how you deal with it, and move forward, not that you made the mistake, that’s been and gone.
Also being comfortable in yourself that you’re not reliant on someone so that if you do have to remove them from your life because they’ve dropped below your comfortable level, you’ll be ok.
I hope that makes sense, I’m not being very articulate. I used to think “don’t trust anyone then you won’t be disappointed” but that’s a really sad way to live. I’m still somewhat guarded but try to find a comfortable level, understand it’s not all or nothing & trust myself to process and deal with the disappointment should it occur rather than be bitter, resentful & withdraw. It’s served me better than the former.