I can't remember the name of the theory, but it's basically that we can be in tact healthy adults, but other parts of us are triggered by circumstances and people at times. There is the wounded child, the joyful child, the nurturing parent, and the punitive parent, as well as some in-betweens. Learning about that was powerful to me like what your T asked you was powerful to you. It takes some self-awareness to practice recognizing which part of you has come out to play with others. I am mostly healthy adult Seriously?, but I am often nurturing parent. It's when hurt child comes out that I run into trouble. I desperately look for nurturing parent in someone else. Very often I am disappointed because most people I interact with are looking for adult Seriously. I understand, too, that pwBPD are mostly hurt child, so me playing nurturing parent, which is a very natural role for me, kind of draws them to me in thee first place. I am sorry to hear you have dealt with depression and rage. I hope you are learning good coping skills from your T.
Schema therapy, very powerful stuff.