Hi Amelia. As Jim said, pwBPD excel at blame shifting. I.e. "you did whatever so that's why I cheated on you." It's effective because there may be some truth in their blame shift. You were upset about her texting someone, which led to an argument (I'm paraphrasing) therefore she feels justified in cheating. I've been in that position and even apologized to my pwBPD for being upset because she was having an affair. How toxic is that? Yikes,
!
About ruminating, or negative thought cycles: I need to make a conscious effort to stop and redirect my thoughts when I catch myself ruminating. It takes effort and practice but it does work. Writing out your feelings in a journal can also be helpful. Although I find I need to write it down and then consciously put it out of my mind until I can sit down and write again.
dt9000