Under extreme and specific circumstances. If you have a controlling and abusive partner who cheats on you and you start an emotional affair just to have some joy in your life and it gets physical then whatever, you're not the bad person. But I also see a difference between forgiveness and moving on. Forgiveness doesn't mean staying together and just because you're staying together doesn't mean there's forgiveness. I can forgive a person for doing something criminal to me but they still have to make amends, even if that amends is never talking to me again. Likewise, there are people in my life who I have to act as though I've forgiven them in order to get through the day but in my heart and mind I don't forgive them and look forward to being away from them/getting even.
Yes. I would rather the first one happen to me. I'd be disappointed to be with someone immature like that and afraid of them going out but If they were intensely remorseful then I could believe it was a genuine accident. The second one is entirely different. The second one is basically being too big of a coward to end the relationship that you're currently in so you start a new one and let it grow till it causes the other relationship to end.
I personally would feel so humiliated and ashamed for taking the risk of being open with someone and having this happen. I wouldn't see the point of being some loser doormat who walks around with his cheating partner like an idiot. I wouldn't want to be around anyone who knew. I'd want to start a new life somewhere else. If they asked me to give them a list of things to do to get my trust back I'd just leave. But if they were throwing themselves at me, constantly checking in with me, constantly showing me their social media/texts/emails/calls and just smothering me all of their own free will and not because I asking them to in order to appease my hurt feefees then maybe. Even then, it just seems like cheating isn't really something you can come back from. Strangers start at zero and have to work to build intimacy and trust from zero. Cheating takes you into the negative. Its almost like a love-debt that you can't truly repay and the person who got cheated on is forever the chump of the relationship.
I'm pretty sure my mom cheated on my dad. When I was a kid my Dad took me into a bathroom and showed me sores on his hip. He said it was herpes and that he'd got it from Mom. He was very serious and calm but I could tell he was furious. Its one of the most shocking memories of my life. Friends of mine who got married got cheated on. I've been so scared of it happening to me that I struggle to have relationships. It just feels so excruciating to work so hard to crawl out of your loneliness, finally get to a place where you're worthy of a relationship, finally find love only to be cheated on. I'm so fucking scared of starting a family in case if fails because of this. I read this reddit a lot trying to learn about infidelity. I've decided that if I get married with kids and I get cheated on then I'm going to divorce and move to another state and start a new family. Which is insane because I created children and now I'm abandoning them but what can you do? Be trapped in a relationship with someone who 'loves' you but can't stop torturing you? I just couldn't handle the humiliation. Also I wouldn't throw away my life trying to 'find closure' I'd just immediately start something new with someone else.
Bottomline for me personally:
Emotional and physical affair lasting at least a week = I'm out. One time physical affair with ex = I'm out. Black out drunk and cheated with random person but called me the morning after totally distraught = I'll work with you.
The biggest thing is empathy. Remember the time you got cheated on and imagine what that partner would have to do to make everything normal again. That's what you're going to have to do.