Terrible childhood, bad genetics, bullying, failing to fit in, failing to find friends early on in life caused me to isolate. While this resulted in some positives, it lead to addictions and lack of social skills.
That leads to BPD. I really would love to be loved, but I have been proven over and over that I am unlovable. So whenever somebody shows me any love, I find it hard to believe, and they probably will realize at some point that they can have somebody better much easier, so don't bother with me. I push them away, because I've had so much rejection (romantic/platonic) that I might as well not bother.
I don't want another rejection, so I keep pushing people away. By doing this, I increase the chance of them rejecting me. At the same time I crave good relationships, so it creates a toxic environment.
I want to be clear that I am never intentionally toxic, it's not some giant plan, it's kind of how my brain works on autopilot:
I want love, love leads to rejection, I don't want rejection.
In my case this also lead to
- hedonism (maximizing fun, additions, escapism, I'll die fairly soon anyway)
- appearing to be selfish (pushing people away, they try for a while and that is boosting my self-esteem, but at some point I push them and they don't come back)
- perfectionism (trying to fit in by being perfect and, to a lesser extend, seeking that in others too),
I have improved a lot over the years, but my most recent breakup is too far, combined with other issues.