Blaming Someone Else

Sure, someone else was involved in this cheating. Your partner cheated with SOMEONE. But to blame that other person is nonsense. Your partner is a human being and in control of what he/she chooses to do or not do. If it hadn't been this particular person, it would have been someone else, if your partner was indeed in the mood to cheat. Your partner has to take full responsibility for not resisting the temptation. There are MILLIONS of temptations out there in the world, and every day most people say, "Sorry, I'm already taken". Your partner did NOT.