Sleep is regulated by two interacting systems: your circadian rhythm (the biological clock) and your sleep pressure (adenosine buildup throughout the day). When these two systems are well aligned, you fall asleep easily, sleep deeply, and wake refreshed. When they're misaligned, everything suffers.
What Controls Your Sleep Quality
The quality of your sleep tonight depends largely on what you did this morning:
- Morning light exposure — Anchors your cortisol awakening response and sets the circadian timer for melatonin release at night.
- Consistency — Waking at the same time every day (including weekends) is the single most impactful sleep habit.
- Evening light — Avoiding bright light and screens after sunset preserves melatonin and makes falling asleep effortless.