Why am i still so quick temper?

Today once again i throw my temper on one of my men for just a small matter. I knew him for about six years and he is my most capable men i have in my team. I just let my temper goes with my emotions. Today is a very tiring job. And what i hate most is that our work is moving in a very slow pace. But why can't i just control my temper. I sure know very well that everyone is already damn tired so is normal for them to complain. I should be more understand. This is also my wrong doing for my marriage. I MUST LEAN HOW TO CONTROL MY TEMPER!