its true. as a person with cptsd (bpd) ive mainly had to resort to giving myself the therapy i need through reading, being mindful every moment of the day (i legit have conversations with myself in real time to decide-what i want to say- vs the impact it will have), and psychiatric medication. The real difficult thing is getting the said person with BPD to WANT to change, and i mean with a desperate fervor, otherwise therapy is basically a silly talk session for me where i jab at the therapist to make them say what i want them to say.

too add an analogy to this, its like building a car with Kinex building sticks, painting it over and making it look like a normal vehicle but driving it is a whole different issue. you cant change the structure under the paint, but you can slowly reinforce every bit of it until its ready to drive on the freeway.