Outsider's perspective: I would imagine that a WAS perceiving a negotiation as "ugly" if the consequences are seen as a punishment, or as a harsh reality of loss that the LBS seems to secretly enjoy (Shadenfrued.)
I would also imagine that if you actually do get "ugly" in those discussions, with a poor attitude or combative tone, it will validate the walk-away and drive him/her further away.
So, I would think it best to avoid any appearance of Shadenfrued, if at all possible. (Even though observing the WAS lying in the bed s/he has made might feel soooooo good at times.)
Lucky
P.S. I'm not assuming that you, Thinker, or any other LBS has done anything overt in this regard. I'm just wondering if there might be some of those feelings that peak out in the tone or body language during discussions.
