I have changed my name to post this as I did have a long-ish affair with a married man, a long time ago.
I hope I am less stupid than I was then, but as to offering an insight, well perhaps I can help a little bit. (I don't expect any sort of validation, it's not a perspective I'm proud to have on the subject)
At the time I had had one relationship of a few years, was still a virgin and was very lonely and pretty vulnerable (mental health issues). I was desperate to be loved.
This man came and knocked on my door and we got talking. He was friends with my neighbour. It was like a switch had been turned on, and I felt very strongly for him.
He seemed to want to do it - to be outside of his familiar life, to break free, he was not happy, his life with his family was great but he felt lost in it I think. Like, the actual 'self' he wanted to cling to, was lost, was not recognised. It didn't fit with how he felt he really was.
Love isn't such a simple thing is it, I suppose - in the relationship I had had, I'd 'loved' the boy I'd been with but at the same time part of me wasn't involved, the sad, unhappy, depressed, loner in me was being pushed to one side, it didn't fit in with this lovely, happy person I was living with, in fact with any sort of positive relationship really.
So I wanted to go and look for someone who recognised that side of me - the tragedy I needed to play out I suppose. I wasn't 'myself' with my boyfriend. I got obsessed with a pop star and realised that I couldn't sustain a relationship with someone so happy and wholesome, and we broke up, though I stopped short of being unfaithful (not that we had that sort of physical relationship anyway, we were very young).
I understood then, the thing about loving someone but loving yourself more. Still though I thought it was very wrong to lie, to be unfaithful. I couldn't justify the married man's behaviour. I wanted us to be together.
My own upbringing involved a mother who was very controlling and didn't want me to spend time with my own father, who was the only person I felt actually liked me. So you can see there was big potential for transference there. In a way, his wife became the representation of my mother, in my head, and he became my father, all the time I was seeking to get him to 'do the right thing' and tell her that actually, he loved me, and wanted to be with me. It was fucked up.
I didn't want to cause any hurt but at the same time, I felt I needed him very much - whenever we broke up, we both crawled back to one another, it was very very painful. He was also playing out his own childhood mess, boarding school at a very young age meant that he was very able to compartmentalise, he had a 'home' and a 'school' and I think sometimes they got mixed up - he had some anger going on towards his parents (wife I suppose) that he wasn't even conscious of.
So it was all massively wrong. I was stupid and inexperienced, he was over a decade older than me, and I was very, very deeply in love. I felt like every breath I took was for him, was to be with him, and he was my first proper sexual partner.
So there is a picture of how it felt. Even now I am ashamed to be in my own skin, for what I helped him do, for what I did. The hurt was never intended but it was kind of irrelevant, to us - our own needs were driving us.
I'd never lied in my life until I met him. I hated lying though it was fascinating too. I felt like this 'love' was worth doing anything for. I was really wrong about that. I feel like I kind of sold my soul. It's not nice and I can never take it back.
Still we are close. He married again (not me) and I still see him. And the other day we looked at each other and I said, you know, we can't take back the awful thing we did, but half of my heart would do it again. The other half is scared of how wrong, how 'evil' I was capable of being. He said he knows what I mean.
I wish I had never met him but at the same time I have never been so happy, so 'complete' as I felt in those days.
It's fucked up and it's horrible. I guess what you can take from this as someone who has been betrayed is that the person betraying you was to blame. Not anything you did - in fact the more 'ok' you are, or were, the more lovely and competent and sound, the happier you were, the more likely it is that they would have needed someone else to play out the miserable, screwed up and deeply wrong side of their character with.