Brink

"Jill's face changed constantly. She was always affectable, always vulnerable. The penalty she paid for being honest was that she lived most of her life poised on brinks. They were real brinks too. At first the sight of Jill poised on a brink scared me badly. I had no confidence in my ability to pull her back, and if I said something false or wrong and she went over she would really go over, into some kind of different life. She never poised on phony brinks."

from All My Friends Are Going to Be Strangers, by Larry McMurtry