Your body runs on a roughly 24-hour internal clock — the circadian rhythm — that governs when you feel alert and when you feel sleepy. Light is the strongest signal that keeps that clock on time.
Why mornings matter
Bright light early in the day tells your brain that the day has started. That sets a timer: melatonin is released roughly 14–16 hours later, helping you feel sleepy at a consistent time. Without a strong morning signal, the clock can drift later, making it harder to fall asleep at night and harder to wake.
How much light
Outdoor light is far brighter than indoor lighting — even on a cloudy day, outdoors is many times brighter than a typical office. Aim for 15–30 minutes outside within an hour or two of waking: a walk, coffee on the balcony, or a commute on foot.
Make it work
- Walk to get your morning coffee instead of making it at home.
- Open the curtains as soon as you wake and sit by a window if you can’t get outside.
- In dark winters, a light therapy box can help; ask a clinician if you have eye conditions or bipolar disorder.
And dim the evenings
The other half of the equation is less light at night. Dimming lights an hour or two before bed helps melatonin rise on schedule.