Chronotype, not willpower, largely determines your natural energy rhythm

Breus argues that the timing of a person's alertness, sleepiness, hunger, and mood swings throughout the day is substantially shaped by genetics rather than habit or discipline, a finding rooted in chronobiology research on the body's internal clock genes. This means that a person who struggles to feel sharp before 10am isn't lazy or undisciplined; their biological clock genuinely runs on a later cycle, producing hormones like cortisol and melatonin on a different schedule than an early-rising counterpart. Breus uses this to challenge the moralizing tone often attached to sleep habits, where early risers are praised as virtuous and late risers as undisciplined, arguing instead that both patterns are legitimate biological variations. He suggests that trying to force a chronotype that doesn't match your genetics, for instance a natural night owl attempting a 5am routine, produces chronic fatigue and underperformance rather than the promised productivity gains, because the effort is spent fighting biology instead of leveraging it.

Takeaway: if a popular routine doesn't work for you, the problem may be a mismatch with your chronotype, not a lack of discipline.