Gmum - To answer your title question, I think the answer is, unfortunately, no. I think that all marriages COULD be saved, if both parties were interested. But in some cases, the other person is too far gone to have any interest. Sometimes, nothing you can say or do or not say or not do will have any impact on the other person's decision. We cant control the other person's thoughts or actions, and if they dont turn around, theres nothing that can be done.
You could come here, DB "perfectly" and fail at saving your marriage -or- you could come here, half-ass it and succeed at saving your marriage. There's no way to really know.
BUT - DBing will improve your odds. AND it will make you a better person on the other side regardless. So, theres really no downside.
