Thanks BFTG, your post was helpful for me and also spurred some introspection for my wife, and we've had some good discussion around it already.
What I really struggle with is the quantity and variation of damaging things there are in my wife's past. The number of painful and humiliating events feels so multifaceted that as soon as my brain finds some peace with one thing, it says to itself, "don't forget about that other thing!" and then the misery starts all over again.
First there's the A, which itself is all over the map from being slutty/NSA/cheap thrill but then also having intimate moments, them going on a date, and worst of all taking a shower together. My mind wants to write it off as either a sex-driven fling OR an emotional affair of the heart, but it seems like both and that's really hard to swallow.
Then, if I ever come to terms with the A, I move on to her next betrayal, telling her colleague about her affair while drinking at a bar, letting him drive her home and proposition her, and letting this asshole stay in our life and attend our wedding and be "friends" with me for years. Sometimes this one feels like the worst of them all to me, even though my wife turned down his proposition. The humiliation from this one is profound for me.
If I can accept that one, my brain moves next to her having her day-long dalliance in England while we were engaged. While supposedly at the peak of her love and commitment to me, she gave herself permission to basically go on an impromptu date with a complete and total stranger in another country. After being approached by this random guy, she allowed him to show her around the town, pull her by the hand from landmark to landmark, put his arm around her at least once, let him buy her a drink, and smoked pot with him. This one hurts so much because we were engaged and because it makes me feel like I have always been out of sight, out of mind for her. I question her love for me, at a time that it should have been peaking. I question the very foundation of our marriage.
If I accept all of the above as "back then my wife had terrible boundaries and was still insanely selfish", then I move on to her crush on her workout partner and her more recent crush on my best friend. These make me feel like I simply do not check all of the boxes for her when it comes to attraction/partner selection. I feel emasculated that my wife has had these fantasies, and it feels like they have happened throughout our entire history (workout partner crush/fantasy was around 2010, best friend crush/fantasy was last year or two).
So to reach some level of acceptance of all this, I have to do a lot of mental gymnastics. I start by basically writing off our entire history as boyfriend/girlfriend, and accept that she was just a horrible girlfriend who was not ready to commit and didn't really know what love was. Then I tell myself that even after getting caught in an A (remember she was walked in on and pseudo-caught by me), she actually did love me but her boundaries were so bad that she could allow herself to have this "date" while overseas. Then I accept that she makes selfish choices and compartmentalizes in such a profound way that having a man who tried to make out with her and new of her infidelity at our wedding is excusable. The after I've cleared all of those painful hurdles, I tell myself that her crush/fantasies are involuntary and not about something lacking in me, and what matters is that she didn't act on them. Finally, I try to accept that the lifetime of lies she fed me were built on love and a fear of losing me rather than just a manipulation to continue using me.
Phew. That's exhausting.
Anyway, this is the general train of thought my mind goes down when I am in my "bad place". It feels impossible sometimes to accept it all, let alone to ever forgive it all. My biggest fear is that years from now I have my own epiphany of "the sum of all of this is that it's a deal breaker", and even more years of my life are wasted.
But in the meantime, I keep trying, I still feel love for her, and our good days can still be very good and feel worth fighting for.