Need to ask about the "Fog" of people in affairs

[GainingStrength]

I need to hear from about the Fog that people get into when they are in affairs because I just don't quite understand it. I've read articles about it, which are helpful as far as they go. However, as much as I've learned over the last five months, I can't understand how an otherwise normal person can become so alien.

A little background: My WAW dropped the bomb on me on 7/6/07. I moved out a week later. Below is a sample of some of her behavior as described in some of my postings:

8/1/07:

W's grandmother died yesterday (long expected) and her mother and aunts arranged the funeral for Monday to accommodate family coming from out of state, etc. Her mother called me first, so I told her I would change my plans for SeaWorld and bring our kids to the funeral. All of this really pissed W off because that's half of her planned romantic weekend with OM, and also she wasn't in on the decision re the kids. I told her calmly that it was my day to have the kids so it was my decision. She backed off, but she did say "I don't know why I should go to this funeral. Nana never did much for me when she was alive."

10/04/07:

My wife is still a "drug addict" addicted to the endorphins from her affair, although she gets angry when I call it that. Funny, she used to lovingly call me her "rock". Then she turned 40, dropped the bomb, and told me she didn't need a rock anymore. Now she needed to "dance", and I wasn't a dancer. Now, she sleeps in our marriage bed with her “dancer”, just down the hall from our daughter.

The above is just the tip of the iceberg. I think you get what she has become. My question is how does a previously caring person become so self-centered, egocentric, and callous? How do they lose all decency and common sense? How does one convince themselves that what they are doing is justified? Also, what happens to make them come out of the fog and does remorse ever set in?

Any insights would be much appreciated.