I was the one who gave the second chance. And it was my husband who needed it. I have always been convinced that there are certain things I wouldn't be able to forgive. But the situation was there and real, I just knew that things can be quite different from how you imagined them. I never doubted this decision or was unhappy with it. It was some kind of wake up call and I was happy to be all in the moment it occurred. I have never forgotten but I have forgiven in our case.
But I knew as well: there won't be a third one. Never. Things can be forgiven/fixed/tried again once; if there is the will to work it out and insight in what went wrong. But if the same happens again, something went so wrong that the persons involved were incapable to learn something out of this experience. And that's where I would draw a line. Of course there can always be new shit going on. But I wouldn't give a third chance for the same thing.
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.