Can a person ever truly earn trust back?

It depends on the person, the place, the thing they did, and just.everything about the incident. I've had some pretty horrible things done to me and if the person apologized I'd give them another chance because I know at heart they are good people. (though some people at heart are bad and I wouldn't give them another chance because of that).

I'm sorry but the trust will certainly decrease. That does not mean I would stop loving them or leave them but to be honest there would always be the awareness, or a reminder every now and then of what they did. They might have the same amount trust even but the minute similar behavior occurs that's reason not to trust them at all. To earn trust back I need the whole truth and they must do what they say.

My now ex and I had troubles about two years before we actually split. He didn't cheat but he came very close to doing it. We decided to try and work things out. We were married and had been together (at that point) almost 10 years. So he said he would do whatever I needed to earn my trust back. After about 3 months, he went right back to acting like nothing had ever happened. I never forgave him. I never fully trusted him again. Every time he was out late or with someone else, I questioned myself. I don't know if anyone can truly earn trust back fully. I don't think for me they can. Once you have lost trust, it is gone. It can't be repaired.