Between two people, it's forgiven out of love that binds. It's knowing that people err & you're not willing to sacrifice a whole marriage over mistakes & bad choices. And some of those will cause a whole lot of pain & suffering. But why end the marriage? It's not like you're given a guarantee that the next person you shack up with will not hurt you in some other form, if not by adultery.
Between me & YHWH, I have forgiveness when I repent & sin no more.
The love that binds comes from knowing God is the author of my marriage. He is the top entity in in our marriage. It's not just my husband & myself. We are in covenant with Him, too.
My husband & I have both caused each other unspeakable pains with some very bad choices that affected both of us when at the time it seemed like no one would be hurt. (I'm not just talking adultery here, it can be anything.) What really got us through was when he made a statement like, "I know I hurt you & you hate me, but can't you hate me later & let me help you with your pain right now?" It may sound stupid (outside the context of the situation), but when I heard those words, they made sense. That is what is meant by "for better or worse." Just b/c there is pain does not mean that love stops. Just b/c a vow is broken does not mean that there can't be reconciliation. We both see that we try so hard to honor the other in all of our thoughts an actions, but sometimes sh!t happens. And we work it through but we always have to go to God 1st to help us get our hearts and our minds right to give us the strength to work together to recover from what injury we caused. But I can't speak for marriages where both parties are not willing to put in the effort to make things work.
I could forgive adultery, but I'm not sure I would not stay in marriage where the other person didn't care that it hurt me & wasn't even interested in trying to stay faithful. One person can not "work" a marriage, they can only remain living in the same house if it came to that.
I guess I'm so adamant b/c we've seen our share of all the possibilities that can strain a marriage & people have been so quick to use the word divorce with either of us. But I believe the working THROUGH troubles is what makes us stronger. Not avoiding & running away from them. There is no growth of character there.
But as I said, it takes two. I can't let an abusive spouse keep beating me until I'm so injured I can't care for my children. I can forgive & divorce to a safe place & never allow him anywhere near me.
I can forgive a spouse learning he's not the heterosexual man I married & divorce him to live his own life (probably still as friends).
I don't know why some people look at marriage as some magic bubble that shields them from life's crisis'. Bad things ARE going to happen. It's up to the couple how the choose to face these times. I've learned I don't need trust people b/c everyone is going to let someone down at least one time at some point in their life. BUT I have learned that I can trust God & He will make my relationships right when those times come.