It’s probably because those people remind you of the people or situation you grew up with that contributed to developing a personality disorder, and/or another trauma after that which exacerbated it, although depending on which one you have that might not necessarily be the case. I have DPD, and I find myself falling back into old habits around customers at my job even though I am actually very comfortable and confident there compared to the rest of my life. As for how to stop, I’m still trying to figure it out myself. The best advice I can give is to keep trying to recognize when this happens. At first you will only recognize it after the fact, but eventually you’ll start the see the patterns as they’re happening, and can start slowly breaking them. Just don’t get too frustrated if you can see the pattern but can’t stop it. It takes time, and having a personality disorder is unfortunately something that will never completely go away.