3 ideas
Every breath in pranayama is divided into four measurable parts: inhalation (puraka), retention after inhaling (antara kumbhaka), exhalation (rechaka), and retention after exhaling (bahya kumbhaka). Mastery is built by training each phase separately and then in controlled ratio to one another, so the breath becomes deliberate rather than reflexive.
Holding the breath (kumbhaka) is dangerous if forced before inhalation and exhalation are smooth, long, and effortless, and can strain the nerves and heart. The retention phase should only be lengthened once the practitioner can sustain it without the slightest jerk, gasp, or loss of evenness when releasing it.
The breath is the one autonomic function that can be consciously controlled, making it the operational link between body and mind. By steadying and lengthening the breath, agitation in the nervous system and fluctuations of thought are quieted, so regulating respiration becomes a direct method for regulating mental state.