Who said that people were excusing or justifying. There are no excuses and no justifications, and having an affair is one of the most regrettable things I have ever done. If I could go back and do things differently, then I would, and if I could prevent someone else from doing the same, then I would.
But the point at which someone is having the affair or has already had the affair is too late to judge, at that point you can only try to understand why and hopefully the person can find the right way and the right thing to do from there.
It is naive to think that leaving a relationship is easy, it's the best thing to do, of course it is, but leaving the relationship if there are major issues is never easy.
In my case I was in an emotionally abusive relationship. He gradually isolated me from friends, in fact he refused to acknowledge that I had friends, he made it difficult for me to go back to work when I wanted to, so I was financially dependent on him. He shattered my self-worth by telling me that he loved me so no-one else mattered, and it didn't matter that the world thought I was ugly/not a nice person/worthless, his love was all that was important. We didn't need a social life because we had each other. he belittled my opinions, if I was talking about something he would talk over the top of me. We argued over sex because of things I wouldn't do, refused to come near me when I was on my period because a hug wasn't enough and he knew he couldn't have sex with me so there was no point being anywhere near me. Everything I was involved in he became involved in as well so I was never doing things he knew nothing about. When I had friends he wanted to know what I was doing, made it difficult if I went out by being moody when I got home so I stopped going out... But this was all subtle over the course of the relationship, and to anyone looking in we were the perfect couple.
But when I met OM he made me feel as if I had worth, for the first time in years. He wanted to be with me for me not for any other reason, or so I thought. And the instant I fell for him was the instant that I knew that I could have the strength to leave my marriage. But yes, regrettably we slept together once, and then I completely checked out of my marriage, never slept with XH again after that, told him I wanted us to split, and told him the reasons why. The OM wasn't the reason, but he was the catalyst . And you know what people said to me when I told them about my marriage prior to the affair? "But he didn't hit you, so it wasn't that bad." So had I left without the affair people would have judged. But instead I had an affair, something which I can't undo, but something which I have bloody well learned from. And in doing so XH's abuse has been written off, minimised in the eyes of even those on here who would have helped me out of an abusive relationship. Even to those I am the lowest of the low, and deserve all the heartache that is sent my way. Have done the unforgivable, and am a despicable person as a result.
If I hadn't met OM I would certainly still be in that abusive relationship, and no-one would have supported me in leaving.
Even the OM told me I was a despicable person afterwards and that he would never trust me. That was ok, I knew it then and I know it now.
The op has already had an affair, it's done. Kicking her while she is down will achieve nothing other than to make the superior posters on here feel even more self righteous.
Perhaps if people tried to understand more why it is that some people feel they are driven to affairs you might go some way towards stopping them from going down the way of no return, and either seeking to repair the issues in the relationship or leave before doing something which they will carry for the rest of their lives.