Reget is a valid question to be asked of me and to ask of myself, but it's not the right concept to accurately describe my frame of mind right now.
Did it cause problems in my life and the lives of others? Sure.
Will I do it again? No.
But, it was a conscious choice I made. I know why I made it at the time and I can own it.
I, now, have to get my life in order again. That sucks. It isn't fun to endure the loss of a companion, the emptiness his absence leaves behind. It isn't fun to face up to fixing my neglect of other areas of life while I intensely poured myself into him. It isn't fun to have to fix the bad habits I picked up as a coping mechanism for the situation, to face work when I feel emptied.
It contained enough pain to teach me some lessons and allow me to see, experientially, why God condemns it.
Like a scary ride at the carnival, sometimes you get off the ride feeling empowered, some times you get off the ride feeling unhealthy and thinking, "Well, I did it, but once was enough for me." and, while the latter is true for me, I don't know that 'regret' is my experience.
I may come to view it differently than I do now but, for now, it was part of my journey, part of what I experienced while choosing to leave my sexual, marital moral structure behind to explore the personally unknown.
I explored and found things out, maybe the hard way, but that knowledge is mine now. It isn't something someone told me, even if what they said was what I experienced. It's knowledge I earned, and knowledge one earns makes one able to approach advising others in a more wholistically helpful way.
I don't think I can regret that.
It's not that I've never advised someone against what I've recently gone through, I actually have. I had a friend, a few years ago, who was regularly engaging in a threesome with her husband and his monogamously married, and thus cheating, best friend.
I adamantly adviced against it from a philosophical standpoint - namely out of Christianity's tenets - from my head, not my experience. And, it wasn't wrong. However, as I went through being what she had been, I thought of her more than once and felt empathy for the emotions she exhibited at the time, but with which I had previously been unable to identify.
Would I still advise against adultery today? Yes.
But, today, I might be a more useful adviser in that I can intimately understand why it's hard to get out of something that has so much emotion tied to it. Because, I got out of something when it hurt to get out of it even though it was the right thing to do.
I held on to my Lover one last time, shaking as tears ran down my face, breathing through the ache in my heart like I was preparing to give birth, until I could put my hands on his chest, look him in the eye and say, "OK, I'm ready."
The thing was wrong, but there was real love there that was hard to let go of.
The thing was wrong, but that man and I shared something beautiful even if everyone else only sees the ugly.
Do I regret being an adulteress? No.
Because I think for me to feel regret, I'd have to ignore the fact that the thing brought several beautiful experiences and useful lessons to me. And, right now, I'm just not willing to do that.