I see my WW in that letter. She's said to me that "I've discovered who I really am and will not change for anyone". I just asked her "who asked you to change other than ending your affair"?
I think that letter hit it right on the head, especially for WAS's who have been married for a long time and were in a generally happy marriage. The affair lets them be all the things they aren't. That's why once the fantasy wears off it most times ends. They aren't "in love" with the OP, they're "in love" with how the OP makes them feel.
I also think that's why exposure of the affair can have such a significant affect on the affair. If the spouse is having those feelings like were described, when reality hits them between the eyes it's sometimes enough to show the fantasy for what it is. To have your kids, parents, the OP's spouse, your best friends, all looking at you it has a way of causing enough internal conflict that it ends the affair.
Just my .02
Hope4us
Me - 49, W 49 S22 & S18 Dday 9/4/07 W claims NC 4/7/08 8/29/09 - Divorce Busted. Lots to work through, but we're going to make it.