Obviously, a failure in a marriage is what brings people here, so both of you made mistakes. The WAS seeks to rectify those mistakes by leaving, having affairs, being generally crappy, and so on. The good DBer attempts to rectify those mistakes by becoming a better person in every way.
When you have spent some time DBing, I think you begin to see the betterment of yourself, realize the efforts you put into becoming the best you can be - and as your own "save-the-marriage" fog begins to lift, then the WAS starts revealing themselves as someone less than you deserve. And not just in words only but you start to FEEL that.
