"Oh, if I could just get through all the emotions that I apparently still have tied up inside me."
The odd thing is.. this is what keeps us all from "winning". You need to focus this idea.. another direction. Take the emotion of "losing" and direct it at him. What do you really loose here? If I say it simply.. you loose someone who does not "care" about losing you. To a point you should not be chasing him around. In a few simple words.. you need to rebuild the "want".
"I was dressed in a pretty dress that H picked out for me last year. I received many compliments on the dress that day, which was nice. H's reaction (well, no compliments but he did sit closer to me while I rocked youngest D to sleep and he played with my knee for a sec)... of course, later he asked if I was eating better and that he could tell that I was b/c he could see it in my arms. (Thanks, now I have fat arms)."
In reading your posts this keeps coming up. Are you really "all that"? You tell us the story of people talking you up all day. Then getting rejected by H. Why does this matter?
Remember.. he does not care about losing you.
.............. It's the persona he wants to loose.
He wants to loose the "little girl" part of you.
"I have new friends, go out lots and still - the idea of my failing M just tends to bring me down."
I remember this. I think more than a few nights I had to excuse myself and go cry somewhere. Looking back.. it still plays to the "emotion" that I carried with me every day. It also points to the fact this is what you need to change.
"Trying to detach, trying to move on... really, really trying."
Detaching.. and Moving on.. 2 different things. Focus on one or the other.
Relax Eat Think Act normal React.. Smartly. Do something different. Emulate. Do Work.