I don't really understand the MN hard line on cheating, I guess I never will.
Without in any way trivialising the very real devastation it can cause, or anyone's individual experience, the cultural level MN hardline on it does seem somewhat out of proportion. Of course it's never right, but not all affairs are the same and they need to be taken in context; an affair doesn't automatically mean that you are a shit human who deserves nothing but eternal punishment. It's also not the only way to wreck a marriage.
There was a thread once where a woman shared her story of how she and her husband had both been in dead marriages, slept together a handful of times and then ended said dead marriages. The wife came round, attacked her and broke her hand. Posters were saying she deserved broken bones, that she should have attempted to obstruct the resulting prosecution by the CPS and that the law should be changed to decriminalise such attacks in such circumstances.
More recently, there have been threads where people have called for adultery to be against the law and punishable by prison sentences or fines (to be fair, they were a minority). There was an eye opener not long ago which showed that for many women on MN, the pain of a betrayed wife and children is completely worth it if it fucks the cheater's life up; that same devastation that is always lamented so much on here becomes entirely palatable, a good thing even, if it's part of a cheater's comeuppance. Lots of people said they'd take pleasure in it. The cheater must be punished at all costs: all other pain to that end is totally worth it, absolutely fine, easy to accept.
One person even drew a parallel between getting involved in a cheater's life, even if they're all practically strangers, and a horrible current case of child abuse and killing. Basically, if you didn't agree with her, you clearly wouldn’t try to protect a child in danger either and revealing a cheat, no matter what the circumstances and how little your connection, was on a par with saving a child's life (so not doing it would be on a par with....). I left the thread at that point.
It is hardcore to the point of blindness and I agree with a PP that this is why it's virtually impossible to have a sensible discussion about it. We get threads like this quite often, effectively just a "but why?" and there's no attempt to understand Amy responses. Dissociation has been explained, but OP still asked "but why doesn't the negative feeling come in the moment?" Because that's dissociation!
And a lot of people will be reading this and assuming I must be a current or past or wannabe OW because there can be no other way to develop any sense of nuance about the whole thing. I'm not.