Reading Gypsy's post, I should clarify an important distinction:
"Letting go" does NOT mean "giving up."
I DO think you shouldn't give up, and you should fight for your marriage and you can tell your wife that you are.
But you should ALSO "drop the rope" as DB teaches, and there's nothing wrong with letting her know THAT, too.
It's a real fine line, but you want to convey "I love you, and I don't want a divorce, but I also won't wait forever. I realize that I can't control you, and so I'm BEGINNING TO move on with my life. I pray you'll make the right decision."