When the man you love, to whom you have devoted your life and for whom you've made countless sacrifices, lies to you and has sex with another behind your back, it is an incomparable anguish.
This is only compounded if you had a good relationship, in which you sought to meet his emotional and physical/sexual needs and make him feel valued and needed.
The only thing to which the anguish comes close is the death of someone you love.
I remember mourning the death of my father when I was fifteen. This feels so very similar to that, yet more painful and complicated.
1. You realize that the person you loved truly is dead to you. What do I mean by this? Well, in my case, the person I thought I married was truly incapable of doing what my husband did. Perhaps the statement's wording would be better put that the person you thought you loved never really existed, or changed in such a fundamental way that he's no longer the same person. I'm no silly girl who doesn't realize how affairs occur and what often triggers them. This is a second marriage for me. I know I did everything right that I could possibly do, and even he admits we have a great relationship and that he wasn't unsatisfied with us. I now realize that I'm married to someone who is not who I thought he was. This doesn't (in and of itself) mean the person to whom I'm married is better or worse than the one I thought I married, just fundamentally different. The person I thought I loved, cherished, and devoted my entire life and soul to either never existed or died out. This pain, well, it is like the shock of death. After someone close to you dies, you go through periods where you almost forget they are gone, and then suddenly it hits you that you'll never, ever see them again. It is this insane-feeling, solid, immutable force that you seem to blindly smack into time and time again as your psyche can't seem to fully accept it. Only time brings this acceptance. The agony, the rage; they are all futile against it.
2. You realize that the person who KILLED the one to whom you thought you were married IS the one to whom you are married. Ouch. This is the hard part. No wonder so many women are so overwhelmed with rage. It isn't so much that the man at whom I'm now looking betrayed me; as it is that he killed the man I loved, killed what I thought we had together, destroyed the "us" that existed, and for such a frivilous reason as shallow self-gratification. I also know he can never fully comprehend what he's done, because he hasn't felt it. Even if there were a "revenge" adultery, which would be stupid, he still wouldn't "get it," because he would feel that he triggered it. He could never comprehend the nature of someone lying to him, deceiving him, gas-lighting him, and sleeping around on him, for no good reason whatsoever if that person was supposed to love him so deeply. He can never comprehend the pain. It is beyond him.
3. The person you're mourning from #1 and the person you're despising from #2 are all wrapped up into one person. Every time I see him, I remember and mourn the man I thought he was. Now I have to learn to love this new, weird person, and I have to alter and reshape how I fundamentally exist within this new relationship. It is either this, or leave.
Right now, leaving isn't an option I am willing to accept. Of course, this means I must prepare myself for what the most likely outcome of staying will be, and I must know how to react when the unfortunately distinct possibility of his unfaithfulness repeating itself becomes real.
In a less poetic fashion, this all sucks, and I am once again in the "club that nobody wants to be in."
~Waving my fragile petals in the dim, grey realm in which the joy of life is always just beyond your reach.~

