Why can't I keep my big fat mouth shut!

Anyone that knows me knows that I occasional have a loud mouth. In definition that means that when I get frustrated in a conversation my brain turns off and my mouth keeps moving. So this happened between me and a person I never expected to do this. So I approached my history teacher and flat out told him I didn't like the book he was teaching from. When he inquired why I told him I thought that it was bias. Why? Well one thing led to another and I don't remember what I said but the next thing I knew I was in the Principal's office. Well apparently I had insulted his teaching skills.... by accident. So he took me to the office told the principal he wanted me expelled and told me he ,"never wanted to see my face again." That left me begging for mercy. I was literally hyperventilating before I left the office. They let me stay but completely rearranged my schedule so I wouldn't be in his class. That's the story of the worst 24 hours of my life. I don't think I will be that stupid again.