Sleep hygiene is not a treatment for chronic insomnia, and the guideline says so explicitly. The American Academy of Sleep Medicine's 2021 guideline on behavioral treatments recommends against using sleep hygiene as a single-component therapy. Not because the advice is wrong, but because it is aimed at a different problem than the one you have.
Which means the months you spent getting the room cooler and the screens off were not a personal failure. You were following instructions that were never going to be enough on their own.
What sleep hygiene is for
The standard list is familiar: keep the bedroom cool and dark, avoid caffeine late, avoid alcohol near bedtime, exercise but not too close to sleep, no screens in the hour before bed, keep a regular schedule.
Every one of those is reasonable. As a set, they describe conditions under which a person who sleeps normally will keep sleeping normally. That is prevention — genuinely valuable, and worth doing.
Chronic insomnia is a different animal. By the time someone has been sleeping badly for months, the problem is no longer about conditions. It is self-sustaining, and it is being held in place by two things that a cool dark room does not touch.
What is actually keeping it going
Too much time in bed
The natural response to bad sleep is to protect it. Go to bed earlier in case tonight is the night. Stay in bed later to catch up. Lie down in the afternoon when the chance appears.
Each of those is sensible, and together they spread a small amount of sleep across a large amount of time in bed. Sleep pressure — the drive that builds the longer you are awake — gets discharged by all that extra lying down, so by bedtime there is less push toward sleep than there should be. Nine hours in bed for six hours of sleep means three hours of lying awake, every night, teaching your body something.
The bed stops meaning sleep
That is the second thing. After enough nights of lying in the dark feeling frustrated, the bed stops signalling sleep and starts signalling this is where I lie awake. Nobody decides to learn that. It forms anyway, the same way any repeated association does.
It is why people with insomnia sometimes fall asleep instantly in a chair in front of the television and then find themselves wide awake the moment they get into bed. The chair carries no history. The bed carries months of it.
What CBT-I does instead
CBT-I attacks both directly.
Sleep restriction narrows the time you spend in bed to roughly the amount you are actually sleeping, then widens it as sleep becomes more solid. Less time in bed means more sleep pressure by bedtime, and a window matched to real sleep means most of the time in bed is spent asleep — which is what unpicks the association. It is the piece doing most of the work in the research, and the piece that makes people feel worse for the first two weeks before it starts helping.
Stimulus control asks you to leave the bed when you have been awake a while, and to keep the bed for sleep. Dull, unglamorous, and the mechanism by which the bed goes back to meaning what it used to.
Cognitive work addresses the arithmetic that runs at 3am — how many hours are left, how bad tomorrow will be — because that arithmetic is arousal, and arousal is the thing keeping you awake.