Confident men don't overreact. In fact, they give little away in their reactions. This is not to say you should focus on being deceptive. But, keeping a calm, cool appearance (regardless of the situation) will make you seem more confident.
Confident men have no reason to lose their tempers or freak out. They know they can handle whatever life throws at them, even the unexpected, and react accordingly. Next time you feel a harsh reaction creeping in, remember to take a deep breath. Pause to reassess the situation from a place of confidence and clarity. The best part? Once you practice this skill, it becomes second nature and reacting calmly will happen naturally.