I hear you! I worked so hard in the marriage for so long, scared to be a housewife who wasn't any longer a wife, scared of what it would do to our kids if we split up. I have been separated from my AH for a year and we are going to legally separate. Even still, I am attached to my marriage, to him, to the dreams and fantasies of what might have been. I love the person my AH used to be and miss him tremendously.
My counselor helped me understand this better. She said that in a marriage, there is a) a bond and b) a partnership. She said I am still bonded to him, but that the partnership aspect is completely gone. A marriage cannot function in a healthy way without that partnership. So now I am working on un-bonding (aka detachment!) from him so that I can get on with my life.