Classic morning lark, night owl, or somewhere in between—your chronotype is mostly genetic. Scheduling life around it instead of against it is the easiest health upgrade you'll ever make. Fighting it is the most exhausting.

Restorative needs range from ~6.5 to ~9 hours between different people. Consistently short-changing your personal number—even by 30 minutes—is often the silent cause of "I sleep 8 hours, but I'm still tired." Maybe you need 8.5. Maybe you only need 7.

How quickly your body clears melatonin determines whether you wake up groggy from a 1 mg supplement, or can take 5 mg and feel nothing the next morning. Slow metabolizers need lower doses and earlier timing. Fast metabolizers can afford more flexibility.

Natural evening melatonin rise varies up to 10-fold between people. Low producers struggle with sleep onset, no matter how good their sleep hygiene is. High producers naturally fall asleep early—sometimes inconveniently so. Light exposure and supplement timing finally make sense once you know your baseline.