I believe it's because of their constant fear of abandonment. In their mind most of the time, it's less painful for them to dump you than have you dump them. They often line up their next supply ahead of time. I know this behavior all too well. Impulsive, irrational behavior is a prime BPD trait. For months following our breakup, I tried to make sense of my ex-g/f's behavior and literally drove myself crazy in the process. Several months ago, I decided for my own mental health that I had to let go of her and stop owning her issues. I went from being the best man she ever dated (according to her) to someone that "made her miserable and dragged her down" overnight. Those words hurt for months afterwards. I could honestly care less today. I know in my heart that I gave her my very best, and I am now content with that.
About 3 months prior to being dumped, my ex told me that she was terrified I was going to leave her. Earlier in our relationship she said, "Every good man that I've ever been with has always left me." She knew that I was concerned about her emotional state, so that's what may have triggered those feelings. Shortly after that, she accused me of being interested in a female co-worker that I was training. This co-worker is over 20 years younger than me and could be my own daughter. I had no interest in that person whatsoever. She kept pushing for engagement, and when I didn't follow through fast enough, I was discarded for the guy that she discarded to start dating me. She started seeing that guy after she discarded her ex-husband and was talking to 3 other men at the same time. It wouldn't surprise me in the least if she was doing the same things behind his back. At least it's not me!
