I like Dobson's book and don't disagree with it completely but parts of it. While I think it is important to draw the line at some point, it gives no room for really allowing the spouse to come back if they are prone to being too proud or embarassed to admit they were wrong.
I actually used a modification of the letter, letting her go.
Me:56, W:51 D:26,S:24,S:22 Married:18 Bomb 9/27/06 Separated 11/27/06 Divorced 10/6/08 Leaving it up to God