I'm not sure if this will help but I have this theory that if you trust yourself then you can deal with the possibility of betrayal without it causing you to distrust everyone. Many people are inherently untrustworthy but many are not. I think it's impossible to live a reasonably normal and satisfactory life without trust, despite all the betrayals we will face. I don't think you can learn to trust... just have to trust and accept the consequences will sometimes be good and sometimes bad. If you trust yourself it will all work out.