My theory... .
They have absolute stranglehold on your emotions. Most of us are just normal people, but people with BPD have an uncanny ability to control your life and just about everything you do. You spend hours upon hours emotionally invested to them, whether it's good or bad. They influence your decision-making, yet you feel like you are major part of them too, only you are a prisoner. This is Stockhold Syndrome that you AGREED to do in the beginning by WANTING them in your life.
The idea of them throwing you away for someone else is absolutely devastating. It symbolizes that you meant nothing. You are still attached to them, which is the reason you are trying to find out about this new girlfriend. It hurts so much to be replaced.
BUT THIS SAYS NOTHING ABOUT YOU!
lolol. You are great person, you just got tied up with the wrong person!
I am at the point where I have stopped idealizing my ex-wife. I made more money, have more friends, was more intelligent in broad scope, and far more talented than she was at anything. She could control and destroy... . that was her strength.
You will get through this. Eventually you'll see the light. I'm starting to. Keep on this site and we'll talk you through it... .