The short version
Lights out: unclench the jaw, let the tongue rest low, soften the corners of the eyes; a barely-there Secret Smile; two slow Trap Doors with a breath between them; a slow wave of release from the crown down to the feet; Backdrop at a simmer. If you wake at 3 a.m.: no clock, no phone, exhale-weighted breathing and the allowing practice, and after about twenty minutes awake, leave the bed.
What the research says
The structure (consistent sleep and wake times, dim light, screens off, leave the bed after twenty minutes awake) is standard sleep guidance and does more than any breathing pattern. Cited under Chapter 11.
Rooms where it does the work
Two rules, no exceptions
Never practice any technique on this site while you are driving, operating machinery, or doing anything that needs your full attention. The slow ones can make you drowsy, faster than you’d expect. And never practice a breath-hold, bellows breath, or any vigorous breathing in or near water. Read Before you begin for the doctor’s list and the rest.
The short version is a reminder, not a lesson. The chapter has the story, the steps, the mistakes, and the limits.