Sympathetic nervous system, division of the nervous system that functions to produce localized adjustments (such as sweating as a response to an increase in temperature) and reflex adjustments of the cardiovascular system.
Breathing is the key to managing your nervous system and understanding how to do relaxation exercises.
Emotions have physical manifestations and they are governed by physical laws. Every action has an opposite reaction. What goes up must come down.
Humans are a naturally aggressive species. Emotionally fit people are those who have learned to channel their anger.