Short map of the protocol, because the jargon is the first barrier and nobody explains it in order.
Sleep diary, week 0. Before anything changes, you track. Rough morning estimates — when you went to bed, roughly when you fell asleep, how long you were up, when you got up. Two weeks of this gives you your actual sleep time, which is almost always different from what you assumed.
Sleep window, week 1. You set time in bed to match the sleep you're actually getting, not the sleep you want. If you're sleeping 5 hours across 8 in bed, the window becomes about 5.5. Wake time gets fixed first, bedtime moves later to fit.
Stimulus control, ongoing. Bed is for sleep. Awake and frustrated, you get up. This is what rebuilds the association your insomnia broke.
Titration, weeks 2 onward. Weekly sleep efficiency goes up, the window expands 15 minutes at a time. Efficiency drops, you hold or trim.
Cognitive work, throughout. The catastrophizing at 2am, the arithmetic about how many hours are left, the belief that tomorrow is ruined. This part gets skipped constantly and it's half the treatment.
That's the whole shape. It usually takes 4 to 8 weeks, and it gets worse before better.
Not medical advice — sleep restriction isn't safe for everyone to self-administer, more on that in a separate post.