Your autonomic nervous system (ANS) controls automatic body functions: heart rate, digestion, breathing, immune function, and stress response. It has two branches with opposite effects: sympathetic (fight-or-flight, activation, arousal) and parasympathetic (rest-and-digest, calm, recovery). Most people spend too much time in sympathetic activation, too little in parasympathetic recovery.
The ANS is called 'automatic' because it operates without conscious control. However, breathing is the one automatic function you can consciously control. By controlling your breathing, you can directly shift your ANS state from sympathetic to parasympathetic or vice versa. This is why breathing exercises are so powerful—they directly control your nervous system.
Optimal health requires balance: sympathetic activation when needed for challenges, rapid parasympathetic recovery afterward. Most modern people are stuck in sympathetic activation with poor parasympathetic recovery. Breathing work that strengthens parasympathetic capacity and allows rapid shifting restores this balance.