What you can do tonight

This is all very easy to understand and intuitive — but it's often overlooked.

• Same wake time every day, weekends included. (An extra hour on Sunday is fine. Three isn't.)
• Daylight within an hour of getting up. Ten minutes outside counts, even when it's grey.
• Last coffee by early afternoon.
• Last drink three hours before bed.
• Last real meal three hours before bed.
• Bedroom cool, dark, quiet — cooler than feels cosy.
• Last half hour: lights down, nothing gripping, phone out of the bed.
• Awake more than twenty minutes? Get up.

Before the why of each item, the why of the list. Two systems decide when you sleep. One is pressure: the longer you're awake, the harder your body pushes for sleep. The other is a clock: your body predicts night and prepares for it, on a schedule it sets mostly from light and from when you get up. Everything on this list is serving one of those two systems — protecting the pressure, or steadying the clock. That's all sleep hygiene is. It's not virtue; it's maintenance.

Start with the wake time, because it's an anchor. Go to sleep and wake at the same time and you'll start getting sleepy at roughly the same hour each night without doing anything else at all. The catch may be a weekend, a vacation, or anything else that interrupts this pattern: sleeping until ten on Sunday feels like catching up, but your internal clock may read it like it would a time zone change. Then, come Sunday night you may not be tired; Monday starts with a sleep deficit. Giving up the “lie-in” is unnecessary — an extra hour won't undo your sleep, though an extra three likely will.

Then there's coffee. Caffeine sticks around far longer than it feels like it does — half of it is still in you five or six hours later, so a four o'clock cup is still working at midnight. Here's the annoying part: it might not stop you falling asleep at all. What it does is flatten your deep sleep. You won't notice tonight. You'll notice tomorrow, and you might blame something else.

Alcohol's impact deserves more than one line in a checklist. That stated, here's the one-line advice: have your last alcoholic drink three hours before bed. Why? It's a sedative, so alcohol will knock you out — but while it's in your system it directly suppresses REM, and you'll likely wake as your body finishes processing it. That's the 3 a.m. wake-up. Learn more in the second-to-last article in this series.

Screens deserve a complete answer, because “no screens” is advice few follow. The light is part of it: bright screens and blue light in the evening push your internal clock later and delay your sleep, because light suppresses the natural melatonin release that should lull you to sleep. But the bigger problem is usually what's on the screen: a show you're gripped by, a feed built to keep you scrolling, an argument in the comments. All of it keeps your brain switched on at exactly the moment it should be powering down. A paper book in dim light doesn't, which is most of why it works better. So keep the television — just move the gripping stuff earlier, keep the last half hour dull, and get the phone out of the bed. That last one is the change most people feel fastest, because the phone is what turns twenty minutes into an hour.

Light and temperature do the rest. Ten minutes outside in the morning gives your clock the strongest signal it gets all day, and dimmer lamps in the evening tell it night is real — a day spent entirely indoors in neutral light leaves it guessing. The bedroom itself is the easy one: cool, dark, quiet, and cooler than feels cosy, because your core temperature has to drop for sleep to start. A warm room is working against you all night.

And one lifted straight from the clinical playbook: if you've been awake more than about twenty minutes, get up. Go somewhere dim, read something dull, come back when you're actually sleepy. Lying there getting frustrated teaches your brain that bed is where you lie awake — a lesson it picks up fast and lets go of slowly. Getting up is how you refuse to teach it.

Last thing, and it matters more than any single item above: nobody does all of this every night. There will be late dinners, flights, deadlines, and bottles of wine you don't regret. The goal isn't a perfect record; it's that most of your nights look roughly like this. Sleep responds to the pattern you keep, not the odd night you miss — if Friday goes sideways, Saturday isn't ruined. Pick the list back up. And give it two weeks before you decide it isn't working. Two good nights isn't a test.