Have you ever or would you ever cheat on the person you're with? Have you dated multiple people at the same time?
I cheated on the woman I was once engaged with. She had a small but existent history of cheating on me that (alongside me breaking it off a few times) lead to being an on-again off-again relationship before the engagement, and that made it much easier to consider overtime. I betrayed that trust over something as simple as masochistic needs, as she was unwilling to deliver that while who I'd found was... more than a talented natural in that area. Being states apart during that stage of our relationship didn't help either.
I found it shameful, but I repeatedly did it with that same partner once she and I couldn't keep our hands off each other anymore. It was one of those "This is a bad idea" sorts of giving in from both sides, as she would be dating people from my unwillingness to break off the engagement. The minute that engagement was canceled she and I went out, so it's hard to feel as bad about it, but it was a matter of her and I's willpower slowly degrading from a series of lustful compromises until we couldn't handle it anymore. Once she realized how sadistic she was, the appetite made her as badly off as I was, plus we'd known each other for a while beforehand so there was a partially shared history that made it easier to be honest instead of play games.
Before that and now I did/do not approve of myself cheating, but it happened then and it lead to something better instead of worse. The worst part about the broken engagement was losing a childhood friend, not even the loss of the relationship itself.