Biddle,
What you describe is partly-associated with
Separation of Stuff. Because people with BPD don't really have a solid sense of self, they allow themselves to be defined (by themselves!) by those around them - as you described.
That said, BPDR is one of the best places on the internet in my not-so-humble opinion because we stay focused on recovery. Certainly no one here can dictate "You should not be feeling that way!" because that's only within the realm of the control of the person experiencing the feeling. We do tend to be on the lookout for transference and/or poor boundaries though and these instances are usually raised in the form of a question. For instance, "You seem quite agitated; is there something else going on for you?"
The racing mind is something that may or may not calm down with the correct medication(s)/med-cocktail. Additionally, the racing mind can sometimes calm down once we feel more secure within our Genuine Selves, once we feel confident in our ability to work with our tools.
I hope this helps - and welcome to BPDR!