When

Since de Mairan’s discovery nearly three centuries ago, scientists have established that nearly all living things—from single-cell organisms that lurk in ponds to multicellular organisms that drive minivans—have biological clocks.

it turns out that caffeine interferes with the production of cortisol—so starting the day immediately with a cup of coffee barely boosts our wakefulness. Worse, early-morning coffee increases our tolerance for caffeine, which means we must gulp ever more to obtain its benefits. The better approach is to drink that first cup an hour or ninety minute

Maybe Captain Turner just made some bad decisions. And maybe those decisions were bad because he made them in the afternoon.

Boost mood: Cardio workouts—swimming, running, even walking the dog—can elevate mood. When we exercise in the morning, we enjoy these effects all day. If you wait to exercise until the evening, you’ll end up sleeping through some of the good feelings.

Endings offer good news and bad news about our behavior and judgment. I’ll give you the bad news first, of course. Endings help us encode, but they can sometimes twist our memory and cloud our perception by overweighting final moments and neglecting the totality. But endings can also be a positive force. They can help energize us to reach a goal. T

Think of this book as a new genre altogether—a when-to book.

Third, at the midpoint, imagine that you’re behind—but only by a little.

Begin by taking two or three minutes to write down what you accomplished since the morning. Making progress is the single largest day-to-day motivator on the job.7 But without tracking our “dones,” we often don’t know whether we’re progressing. Ending the day by recording what you’ve achieved can encode the entire day more positively.

Let’s begin with personality, including what social scientists call the “Big Five” traits—openness, conscientiousness, extraversion, agreeableness, and neuroticism. Much of the research shows morning people to be pleasant, productive folks—“introverted, conscientious, agreeable, persistent, and emotionally stable” women and men who take initiative,