I started typing out a comment to this post by Paul, but it turned out to be so long, that I figured it needed it's own post.
Paul wrote the following with regard to people who cheat on their partners:
"if you were so incomprehensibly foolish as to freely, and while sober, promise someone that you will remain faithful to them, then you should remain faithful to them. No excuses. You made the promise. Keep it.
That's Plan A.
In life, Plan A doesn't always work, and so most people always try to have a Plan B. Here, then, is Plan B: If you do cheat on your partner, then do so in the most ethical and responsible manner still possible."
In one of the comments, brandone stated:
"I think that anyone with the self-awareness and conscientiousness to successfully pull off Plan B also probably has the inner resources to hold fast to their promise from Plan A."
In principal I agree with brandone. But there is more to it for me than that. I also firmly believe it is the responsibility of the person making the promise to keep it. Therefore, if person A cheats on person B with person C, then person C cannot be blamed for this. Person C never made any promises to person B, but person A did. Does this make sense? It is fully person A's responsibility to keep his/her promise.
Having been around the block a few times, I know that if I feel a strong desire to cheat on my partner, there is something inherently wrong/lacking in my relationship and would consider that serious cause to break up.
Nothing is more important to me that the need to trust completely and be trusted completely. I would therefore also question the long-term viability of my relationship if I felt I had reason to be jealous (i.e. was worried about the possibility of my partner cheating).
I was in an extremely abusive and controlling relationship for several years, and both my son F1-1 and I am still paying a very high price for that. I will no longer put up with jealousy from my partner, it is simply an indication of lack of trust. This "I'm only jealous because I love you so much, you should be worried if I don't care any more what you do" is utter nonsense. And how about "I trust you, just no one else?" Bullshit. Cheating takes two people, and if you can't trust anyone with me, you don't trust me.
Don't get me wrong. It's not that I don't find anyone else attractive, it's just that I choose not to act on it. In fact, I have found it is a great diffuser of any feelings of attraction to a "person C" to just tell my husband about it. "Hey sweetheart, you know, I think person C is very cute." Suddenly a level of mysteriousness and secrecy disappears and the attractiveness changes into something funny, and my husband and I can joke about it.
In short. If you promise not to cheat, don't. If you can't keep your promise, you shouldn't be making any promises. And then maybe you simply don't belong in the relationship you have.