Kaigress
Getting so lost in your rant that you forget what you were mad about and start yelling about something else that makes no sense.
He was mad about the wrong password, then he remembered he didn't take his meds and now he's mad about that.
She was ranting about her cat, then she remembered she had a bad day at work and now she's ranting about that.
I was angry about my coffee, then I remembered I didn't feed my fish and now I'm angry about that.