So, I had a tryst with a married man. I thought better of it eventually and ended it, but his wife still found out. And recently, she wrote me an email. I don't know his wife at all. What is my responsibility here? Do I write her back? Should I stay the f**k out of it (even though clearly I'm already involved)?
Stay out of it. No good could come from corresponding with his wife, and it will further complicate an already messy and fraught situation. Nothing you could possibly say to her would undo the damage of the affair—not apologizing or explaining or showing remorse. Your responsibility is to remove yourself from the situation completely. That's the humane thing to do. He did a shitty thing. You did a shitty thing. Accept your role in that, and try to conduct yourself with as much integrity as possible. Whatever happens to their relationship, it's up to them to deal with the fallout now—hence the whole, "Til Death Do Us Part" contract, which you did not sign.
It's natural for the spurned party to want to reach out to you. Infidelity brings out a wildly complicated set of emotions (rage, jealousy, anger, insecurity, fear and doubt). She might want your side of the story to see if her husband is lying or misrepresenting what happened between the two of you. She might want to shift some of the blame off her partner. She might want to make you feel guilty or ashamed. She might want to talk to you out of simple, masochistic curiosity. Who is this other woman? How do I compare to her? She might think corresponding with you will give her a sense of closure. Hell, you might want closure as well. But if that's the case then I urge you to seek it elsewhere. Ultimately, any issues she has should be taken up with her husband, not a stranger.
It sounds like you probably know this, but if you haven't done so already, cut off all contact with him. No texts, emails or phone calls. If you do see him out and about, be polite, but that's it. Be steadfast in your convictions, and you won't repeat your mistake.
I'm not going to harp on you for having a "tryst," as you say, because I don't know the circumstances, and it's far too easy to make blanket statements about cheating that villainize all parties involved. The reality is we all make less-than-stellar relationship choices, no matter how smart or ethical we may be the majority of the time. The clichés are sometimes true. We have to play with fire to understand getting burned. The real test is what we do afterward, how we move on from these choices, and how they alter us for the better.
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