I struggle with this as well. My mom suffers from pretty severe untreated mental illness (paranoid schizophrenia) and interactions with her are a huge trigger for me. I spent a lot of my childhood trying to manage her erratic moods so that I would feel safe. When I'm around her I have to force myself to shut off the fixit mode and remind myself that her bizarre responses to everyday interactions are not my fault.
I said the word "dog" today and it set her off on a ten minute rant. I pretty much had to force myself not to react or respond in any way. Afterward my brother said, "Well, you shouldn't have said the word 'dog'."
I said, "The words I say have nothing to do with her symptoms."
And it's true. Even if I walked on eggshells 24/7 and watched every word out of my mouth, it wouldn't matter. She is mentally ill. It has nothing to do with me.
That was a huge revelation.
"It has nothing to do with me." I've had to make that my mantra. It helps.