Can your students tell whether you are calm, upset, tired, or impatient? They read you like a book! They know even without you speaking, because they read your body language.
Do your students know how to push your buttons? Do they like to be in control? Do they want their own way?
How can kids tell when they are in control? Consider the following questions:
When you are calm, who is controlling your mind and body?
When you are upset, who is controlling your mind and body?
When you are calm, you can think. You can use all your intelligence and experience and all your social skills to deal with a situation. When you are upset, you react. Instead of thinking, you have a fight-flight reflex.
Have you ever said something in the heat of the moment that you wish you could take back? Thinking comes later. When you are calm -- when you have time to think -- you can manage a situation.
Classroom management requires calm. You never will be able to manage another person's behavior until you can manage your own.