Wow I didn't expect so much feedback on this poll, some of your stories of past experiences, I hope you managed to find happiness after the issue was dealt with
Personally, I've been cheated on, gave a second chance, and it continued to happen. After that, my own strict rule is, if you cheat, I don't care who it was with, how I found out, or what you say after the event, you're gone. In my own personal opinion there is no excuse for cheating, a relationship is a bond, and if you feel you need to cheat on your partner you should break up with them because clearly you don't love them and don't want to be with them.
However, there are some cases where I've had friends who have cheated and despite the fact that they did it, it was not for lack of wanting to leave their partner. One of the friends in this case eventually got a restraining order placed on her ex, but she feared for hers and her child's life (not a child by him) if she were to leave him, and she met someone who made her happy. That's where I feel cheating is ok, if you literally have NO way out of the relationship without physical danger to yourself. But otherwise, break it off :/ that's why, I say, no 2nd chances!!!