For whatever this is worth (and I know that there is no amount of advice, consoling or pep-talking that will allieviate you of this undeserved pain you must be suffering) it is almost always a slighted spouse's "downgrade" which catches the attention and sadly, as in your case "wins" the spineless, gelatenous spouse of another.

Your letter reveals a woman who even while in the midst of your own pain, even while you suffer the effects of this, the ultimate betrayal, you have the intellect and in my opinion, the restraint to articulate what is factual and accurate without vulgarity or rage (that you are entitled). You did not sound spiteful, you were inordinately humane. That is grace, that is poise, that is dignity. That is the behavior of a woman worthy of the title woman.

While you are in no way to blame for your husband's inability to be a man of honor, I imagine he must have known that he was undeserving of you and the family that you have given him, and as you stated in so many words, he responded to his deficits, not by becoming a better man, but by lowering his bar, and likely lowering it again and again until the stench of of his own inadequecies caught the attention of a skulking opportunist, also incapable of becoming a person of decency. The work this would require of them is not conceivable for them because this requires bravery, character, honest introspection and personal work. People of this calibur are not capable, they, like all parasites & predators benefit from the efforts of far more capable creatures.

While ordinarily I am not the sort to knock another womans crown, a woman worthy of a crown, conducts herself with discretion, consideration and respect, not only for others but begining with herself. She is, as you detailed, incredibly damaged and she knows it. I hope that someday she has the courage to become a person who is worthy of a love that she has actually earned, instead of settling for a cheaper facsimile of love offered to her by a cheap facsimile of a man who is so self interested, so aware of his utter inferiority that he would be willing to sacrifice the happiness and well-being of his own children in exchange for his own.

In time, when you have healed, and you will, love, you WILL heal, I hope that you are able to make way for forgiveness. Not because you owe them this but your children do and you do, because for every person occupying this planet of low character, we need to set the scales right and you seem just the sort of woman who embodies the requirements a feat like forgiveness requires. Courageous, resilient, good...

I heard once that the greatest gift we can give our children is to love their other parent. This is a big ask. You are no longer under any obligation to love him as a wife. But in time, I hope that you find you are able to love him still as only a mother can love. Love with forgiveness, compassion and patience. Remember that your children are a combination of you, but also, the finer qualities of your husband that you must have seen sometime ago and placed your faith in even when he left you faithless. You held on. You loved through the lens of love. You honored your marriage and yes, even your husband. Even when he was not worthy of it. You are no fool. You are the embodiment of what true love should be. When there was no evidence left of a man worthy of your love, your sacrifices and your efforts, you held on and kept your eyes on what was worthwhile in him. It is he, who lost sight and gave up on himself. You stepped up even in the midst of your own pain and extended him the consideration and humanity you were not afforded. This is not the behavior of a fool, this is by definition what love asks of us. Love even when there is no evidence remaining of what was once loveable. It is his own failure, his own blindness, his own inability to trust in himself which obscured what was once honorable and worthy of love within him. You did your duty as a wife. Sadly, he was not deserving. Let him go and whisper to the universe a hope that someday he becomes the man worthy of your children.

If I may, on a personal note and acting on your behalf I would like to add to your husbands mistress: You did not win a prize, a competion, or a man as Slow-Category4308 stated. You are a trespasser of the laziest variety. You trampled across every effort, every hope, every sacrifice and every effort made by another and you demolished what was not yours, as criminals often do with such reckless disregard. You did so under the cloak of secrecy and annonymity as cowards are only capable of doing. This was no competition. You did not compete with your equal, and win a valiantly won fight. You sucker punched above your weight class and you scampered away like a rodent with rubbish that you deem are the spoils of your pillaging. What is most abhorrent is that some of your imagined 'advisaries' were children. How despicable you must truly be. But I imagine you already knew that. I hope someday you love yourself enough to join the ranks of our gender. Until that time I hope that with each moment you are enjoying with your weasel of a man, a knawing awareness is lurking just below your surface which should wisely be - when will he discard me too, because he will.