How does mindfulness practice improve psychological and physical well-being? By stimulating the parasympathetic nervous system (PNS), which controls many automatic and involuntary actions as well as ones like breathing that can be consciously directed by the mind.
The PNS has a “rest and digest” function that promotes a slower heartbeat, slower respiration, and relaxation. It gives a break to the sympathetic nervous system (SNS), which controls the “fight or flight” response that releases adrenaline and impairs digestion, sleep, and mental health.
The SNS is like the accelerator pedal on a car, whereas the PNS is the brake. A well-functioning vehicle needs both, so you can slow down and speed up in roughly equal measures.