I posted this somewhere else in an effort to explain to someone without BPD what it is like having BPD. Im wondering if anyone else can relate? 

"A good way that I like to describe it is as follows: in life, everybody is a marble. Some marbles are green, some are red, some are large, some are small. Whatever the type of marble, a normal and healthy marble knows exactly what color, shape, size, etc. they are. Except for me. I'm not a marble. I'm a 2d shaped circle in which things pass through easily. Today, you can place something inside the circle, and I'll define myself by whatever you place inside me. Tomorrow, someone could place something completely different inside of the circle, and then my view of myself will change immediately to fit whatever has been placed in that circle. If a red marble tells a green marble that he's not green and is instead red, then the green marble may be irritated or annoyed, but he will know deep down inside that he is green and not red. However, with me, I don't know who I am or what is inside of me."