So many here, including me, tried to find answers to which there were none. Why did they do those things? Why destroy everything like that? Why behave in that way? The answer is of course, they are disordered and it's what they do! This fable helps me remember, that it's not to do with me - it's just the way they are, and all I can do is accept it. Expecting a BPD to behave logically is like expecting a scorpion not to sting.
A scorpion, being a very poor swimmer, asked a turtle to carry him on his back across a river. "Are you mad?" exclaimed the turtle. "You'll sting me while I'm swimming and I'll drown."
"My dear turtle," laughed the scorpion, "if I were to sting you, we would both drown. Now where is the logic in that?"
"You're right!" cried the turtle. "Hop on!" The scorpion climbed aboard and halfway across the river gave the turtle a mighty sting. As they both sank to the bottom, the turtle said:
"You said there'd be no logic in your stinging me. Now we both shall perish. Why did you do it?"
"It has nothing to do with logic," the drowning scorpion replied. "It's just what I do."