Light is the lever

If you change one thing after this course, change your light. Not your mattress, not your supplement shelf, not your bedtime. Your light.

What light is doing

You have an internal clock that runs slightly longer than twenty-four hours and gets reset daily, primarily by light hitting your eyes. Morning light pulls the clock earlier, making you sleepy sooner that night. Evening light pushes it later, making you wide awake when you’d rather not be.

That’s the entire mechanism, and it’s remarkably powerful. It’s also why the same person can be a “night owl” in one job and not in another.

The morning half

Get outside within an hour of waking, for ten to twenty minutes. Overcast counts - outdoor light on a grey day is still many times brighter than a well-lit room. Through a window doesn’t work nearly as well, because glass cuts the intensity substantially.

This is the single highest-yield sleep habit there is, and it happens before you’ve done anything difficult.

The evening half

For the two hours before bed, get dim. Not screen-free necessarily - dim. Overhead lights off, lamps on, and lamps low. The goal is a room that looks like evening rather than a room that looks like an office.

Screen brightness matters more than screen colour. A phone at minimum brightness held at arm’s length is a small input; the same phone at full brightness six inches from your face is not.

What about blue-light glasses?

They do something, and it’s smaller than the marketing suggests. Turning the lights down does more, for free. If you work nights and can’t control the lighting, they become a reasonable tool rather than a first resort.

You cannot decide to be sleepy. You can arrange the light so that sleepiness arrives on time.