Trust isn't just about me being trustworthy but also about others making a decision to trust me.
I messed up a relationship real bad once...bottom line, if he couldn't come to terms and trust me again....there was no point in continuing in a relationship that was no longer healthy.....
I try to change and act in healthy ways, and I try to give it time. Most time's that works, but if the damage is too severe or the other person isn't willing to heal....then a time comes to let go and move on.
(my ex sponsor and I went through this...we aren't "enemies" and talk occationallly, but it doesn't appear that the damage can really be fixed to the point of a really close relationship)