You had some mental issues. Sometimes you just couldn't control yourself but most of the time you were just like a quiet shy kid standing in the corner. Despite your age and strength you liked just being quiet.

Zuko was new so he didn't know what things made you explode. He got into a fight with Katara and started yelling cuz Katara called him lazy and useless.

"...OHHH PLEASE AND WHAT DO THEY DO IF I DO NOTHING!!?" He yelled pointing at you. You were on the werge of attacking.