Why does expressing anger gets beyond our control?

The mistrust in the family (2 brothers and 2 sisters living with our mother) is not dissolved as yet. My prior service in the prejuced and under paid Pakistan National Guards makes them think that I am a useless man. Even our 20 years old sister does not seem to respect me. 2 days earlier I just burst out on her as she wanted me to leave the room where our mother was sitting and I just went to talk to our mother. Our sister has a habit of studying while sitting right among others. I got mad at her as it is like 2 years after my release from the army and I am facing such a behaviour from them. I called her names twice or thrice. And then felt like crying for doing this. She was the one whom I had carried in my lap when she was a child. I may never forgive myself for saying these things to her.