How did you learn as an adult?
With infinite patience, compassion of love from two women - my grandma and my girlfriend (who later became my wife and the mother of my child). And LOTS of therapy (CBT).
Why hurt another in the first place?
I don't know.
Because it's all we've ever known. We don't know how to be kind.
Because we believe that we are evil, and if you believe it enough, you act it. And hurting you reinforces that belief.
Because the alternative - being vulnerable - is just to frightening.
And then there is a thing called "splitting
" - seeing the world in black and white. It is a symptom of BPD but I understand that it is also something that can occur in people who are not quite diagnosable with BPD. If you hurt me, whether intentionally or not - you instantly become evil and I can no longer remember anything good about you. I lash out at that evil person, determined to hurt and get my revenge, determined to protect myself from further hurt by driving you from my life. Then you break down and cry and say you love me, and suddenly you are good again. I can no longer remember anything evil about you and I am terrified of you leaving me because I cannot live without you...
I hate you... don't leave me!
Yes, love - the pain and remorse for hurting you is real. It feeds on his self-loathing and feeds into his self-loathing in turn, creating a vicious cycle. When he hurts you cries out of remorse but also because it confirms that he is as bad as he things, and that is incredibly painful. I'm not sure how, or even if, you can break that cycle without professional help.