Thanks, CityGirl, for your comments and for sharing some of your personal experience with a sobbing and guilt-ridden H. I'm sorry for your experience, but I'm relieved to know that my case is not terribly rare or unusual.
I think my H may fall into the category you described as "so far gone they don't even know what a state of depression they are living in." That pretty much sums it up for him. He doesn't think there's anything wrong with him, which is why he hasn't done anything to help himself. The fact that he quit taking his medication means nothing. Evidently he was miraculously cured and no longer needs the medication. The real source of his unhappiness is--you guessed it--me! Not his chemical imbalance and family history of it.
Thanks again for your thoughts. Stop by again any time.
