Nothing sets your body clock like light. Get it right — bright by day, dim by night — and half of sleep looks after itself; get it wrong and no pill will fully rescue you.
Get bright light into your eyes soon after waking, ideally outdoors (even an overcast sky is many times brighter than indoor lighting) for 10–30 minutes. Morning light anchors and strengthens your circadian rhythm, making you alert now and sleepy at the right time tonight. It's the single most powerful — and completely free — circadian tool you have. Evidence ●●●●○
In the last 2–3 hours before bed, dim the lights and cut bright, blue-rich screen light, which suppresses melatonin and pushes your clock later. Use warm, dim lamps, night modes, and low brightness. Blue-blocking glasses may help a little, but the evidence is genuinely mixed — don't over-rely on them; simply dimming everything does more. Evidence ●●●○○
Even light through closed eyelids matters: a controlled study found a single night in a moderately lit room raised heart rate and worsened next-morning glucose handling versus sleeping in the dark. Kill the standby LEDs, block the window, and mask your eyes if the room can't be made fully dark. Evidence ●●●○○
The two-line light protocol
Bright light in your eyes within an hour of waking; dim, warm, low light for the last few hours before bed. Do just this and your sleep timing improves on its own — no device required.
The Sleep Guide