I fell in love with someone else after being in a dreadfully unhappy marriage for 10 years and having tried everything I could to make it work.
I do regret it. My dh guessed what was happening only 2 weeks after I had met the other man, and I admitted it all. He threw me and the children out and has made my life difficult ever since (this was more than 5 years ago now).
I continued the relationship with the other man for several years before I realised he was totally wrong for me and that I had fallen for him because I was desperately unhappy and unloved at the time, and that he appeared to offer everything I felt was missing from my marriage.
Of course I should have ended my marriage before embarking on any sort of relationship with another man, but I admit I was too cowardly to do it, so I (only semi-consciously) manufactured a situation that would force it to end.
My husband was a rotten, rubbish husband who let me down very badly during the time we were together, and yet, by having an affair, I handed him a reason to blame everything on that, which did neither of us any favours - he has been unable to see beyond what I did "to him", and I have been forever cast as the villain of the piece. He has not held back from voicing his opinion of me to our two children, which has affected them badly too.
My advice to anyone considering having an affair is that however awful the prospect of ending your current relationship may be, it is not as bad as facing the consequences of being caught. Even if you are not caught, you will feel shit about yourself for deceiving the other person and it will be difficult if not impossible to ever find a way back. Relationships are about trust - having an affair, whether it is discovered or not, destroys that bond one way or another. The only true way back is if your husband/partner knows about the affair and is prepared to forgive.
Voice of bitter experience who ought to be in bed