Beneficial relaxation only happens when you can shift out of the sympathetic nervous system and into the parasympathetic nervous system.
The sympathetic nervous system, along with the parasympathetic nervous system, are part of your autonomic nervous system.
Sympathetic is full on stress, while parasympathetic is relaxed and present.
The sympathetic nervous system prepares the body for physical activities and is often referred to as the “fight or flight” response. The parasympathetic nervous system has an opposite effect and relaxes the body to inhibit or slow down many of the body’s high energy functions.