What is something that really makes me angry?

What is something that really makes me angry? I would have to say it’s a know it all. I’m sure we have all known a few of those in our time. The person that no matter where you have been they have already been there. Someone that no matter what you are talking about they can find their way into your conversation and tell you a little something about what you are saying. It’s always funny, or not, that whatever the subject is a know it all will have something to say. I find this behavior very rude and it really makes me angry. I have a roommate with this exact behavior issue. I entertain friends on occasion, and every time my best friend is in my home, it’s a guarantee that my roommate will show this side. Sometimes I have to step in to calm the situation. I have brought this bad behavior to my roommate’s attention many times, and it doesn’t seem to help. I guess the old saying that bad habits are hard to break is true.