Hello. I can relate to what you are saying. My partner of almost 2 years have BPD and when we have arguments, it is difficult to not take things personally. What I suggest is to practice on thinking logically so that you can approach the situation in a logical manner and instead of reacting, respond to the argument by asking the person a logical question. For example, when my partner says hurtful things to me, I would say, "Is that helpful?" And my partner have apologise. Also if you are not tight on budget, I suggest going to a dual counselling where the counsellor is specialise in schema therapy. The schema therapist would recommend the two of you to attend once a week or once a fortnight because the therapist would give you ongoing practical homework for you to do outside of the counselling session to help improve your relationship