Nuancing my last post, an ongoing affair would be a lot more stressful for me than a one time thing. I think that's a lot more dependent on my moral compass than on me being an Aspie.
I make the distinction between a one time thing and an affair because I believe people make mistakes. I'm not advocating cheating as okay, but I think people can get bored in long-term relationships and the thrill of someone new that's attracted to you can be tempting. Maybe your partner has been distant lately, or your sex life has fizzled to non-existent. I'm also not saying alcohol is an excuse for betrayal, but it can definitely be a catalyst for lustful feelings that are already brewing.
I've cheated as a one time thing before, and I've been cheated on this way as well. It's a ****** thing, whether you're cheating or being cheated on, but so long as it's a one time thing it's not the end of the world to me. It merits some soul searching, but it doesn't irreversibly land you in the category "worst people ever" in my book.
Having an affair means, to me, actively and consciously betraying your partner, not just physically but also emotionally, for an extended period of time. I couldn't deal with this because:
A) I would question my relationship to my partner, wondering why I would continue dating someone when I obviously crave outside attention.
B) I would figuratively die from heartbreak and embarrassment if I found out my partner had an affair, I wouldn't want to inflict the same feelings on him.
C) Relationships are built on trust and I would succumb to overwhelming guilt over violating the trust between me and my partner by actively seeking out someone else.