I don’t know why but I often to to my self is it halal to do that and I say bad words while I talk to my self is it haram
Anything which you do and have bad effects your physical or mental health is haram in Islam. Bad words create bad feelings and intentions which leads to bad actions. If you are saying bad words about you it will cause depression and disappointment. If you are saying bad words about others then it will cause fights. And bad words are coming from bad thoughts
Hazrat Ali RA says "As water drops make a river thoughts make character and faith"