In the same vein as the guy who said he's posting from the cheater's perspective, I'm going to offer another, more positive story from a cheater's perspective.
My boyfriend and I were dating for a few months when I cheated on him while he was out of town for an extended amount of time. Our communication was poor, we didn't make it clear what either of us wanted or expected, and he would consistently ignore me. I got scared and hooked up with a guy we both worked with- someone he knew and was already jealous of, and who I had already hooked up with before. I was ashamed that I acted on my insecurity and needed the validation of someone else wanting to have sex with me to feel worthy.
By the time my boyfriend came home, I was expecting him to break up with me, so I mentally buried the incident. Turns out he was just pushing me away because he was scared as well. He wanted to stay together, and that's all I wanted, so I never told him. He didn't find out for a few months until a mutual friend told him. I honestly don't know when I would have told him, since my frame of mind was that he was going to dump me. I never intended to hook up with the guy again because I had the security of the relationship.
It was really, really up and down for 6 months. He cheated on me with his ex-girlfriend soon after he found out. He tried breaking up with me twice, but I really proved to him that it was him I wanted. I quit the job where we both worked, made my boundaries very clear with a lot of people in my life that I had hooked up with before we were dating. It was NOT easy convincing him that he could trust me, but now, a year after everything, we live together and do not plan on breaking up.
It still comes up. We've had really bad fights, and he has a lot of anxiety and I have a lot of guilt. But we both feel the relationship is worth saving and feel secure.
Had he not taken me back, I wouldn't have been able to date for a long time. I would have been afraid of hurting someone again and closed myself off.
It is possible to create trust again after a cheating incident. It takes a lot of understanding, empathy, and believing in each other.