It has nothing to do with bipolar or any other mental disorder. Dwelling on negative comments is actually completely normal. In fact, it may even serve an evolutionary function. One needs to be made aware of people who are not trustworthy. Of course, there are times that this adaptation can backfire on us whether you have bipolar, another mental health condition, or no mental illnesses at all. There are times when someone may have said something in the moment and it is simply never forgotten. One looks at the person in a negative light, despite them having made many positive comments and done many good things. The past couple of years, I have been like this very bad for some reason.