I just wanted to make a comment because I see a LOT of posts that invalidate the very real feelings people can have for the OM or OW. Yes, even in cyber relaionships, feelings are often "real." Posts that say "they are in la la land" or "he says he loves her, but he knows nothing about real love." Who does? Love is a poorly understood concept in general, and married people have no patent on it.
I think that in order to win the spouse back and make it LAST, it is VERY important to try to imagine the kind of love that often exists in an affair. Because this type of idealized, passionate, heady, often very emotionally intimate love is a human need for most people, and sorely lacking in a lot of marriages.
"Affair love" or ANY new love for that matter, is high in UNCONDITIONAL POSITIVE REGARD. Not many marriages are "mutual admiration societies," and they should be! They should be more like affairs! It's a beautiful thing! Some marriages were never sufficiently like that even in the beginning, for a multitude of reasons, so it's hard to "get back" to where something never was in the first place...
So when a spouse says "I have more passion/natural chemistry with the OM or OW," that feels painful to the spouse, because they feel there's nothing they can do about that. But really, is that true? I'm not so sure. I think passion is mostly about being overwhelmed with your own good feelings, and that can be a CHOICE in a marriage, to a great extent. And it's CONTAGIOUS. Of course some of that "passionate" affair feeling is fueled by the illicit nature of it, and even that spirit of "illicitness" (naughtiness) is an important human need! It's the cornerstone of "eroticism" and marrieds need to find a way to put naughtiness into the marriage, safely. There are books on how to do that.
H's and W's need to re-enchant themselves with their mates... not carry on about what a jerk the OM or OW is. They are doing something right, if they have your H or W in their arms!
Sure, affair love is not usually as "deep and meaningful" as the more gounded attachment that develops in a long marriage, but just because it may be different than that does not mean it is any less IMPORTANT! And, it probably has just as much potential to be deep and meaningful in time! Some people do leave their mates for the OM or OW and are happy with them in lasting relationships, so it's only the AFFAIR that is "illigitimate" NOT always the feelings! Cheating spouses who want to return home often downplay feelings for the OM or OW but this is often just a way to "re-frame" their feelings in a way that causes less internal conflict for them and their mates.
I think if H's and W's stop "dissing" (disrespecting) the stuff that affairs are made of, and start trying to figure out how to put those critically important things back into the marriage, it would be a more mature way to look at it. Just some food for thought.