Your time on Earth is precious and limited. Here’s how to waste it. The other afternoon, in an effort to avoid doing my work, I picked up Henry David Thoreau's Walden. It turned out to be a fitting choice, as Thoreau has quite a bit to say about wasting time. "The cost of a thing," he wrote in Walden, "is the amount of what I will call life which is required to be exchanged for it, immediately or in the long run."

Thoreau's point is not that we should be all work and no play—he was one of history's most prominent critics of that way of living. Rather, he argued that we waste too much of our lives on things we don't value. Without thinking about it, we are spectacularly failing some cosmic cost-benefit test, as measured not in money but in what matters most: time.

This argument is hard to refute. Many of the pastimes on which we while away huge portions of our lives feel good in the moment but bring us anxiety and regret when we manage to tear ourselves away. The average American spent three hours and 43 minutes every day watching live TV in the first quarter of 2020, according to Nielsen. That's a lot, but still less time than the three hours and 46 minutes people spent staring at their smartphones.

I am not arguing that non-work activities are necessarily a waste of time; quite the contrary, there is plenty of evidence that time spent daydreaming and enjoying non-work pursuits can lead to not just happiness but also better work performance and higher creativity. There are really only two ways that time can be truly "wasted": when you engage in something that crowds out more productive or edifying activities, and when you deliberately engage in something that, on balance, you don't actually even like. These instances of wasted time can be a source of anxiety and regret, but in reality, they are a valuable resource: If we train ourselves to avoid wasting our minutes, we will have discovered a new reservoir of time that we can use in joyful and productive ways.

We all have frittered away time on one thing at the expense of another, more valuable thing and kicked ourselves for it later. I once stayed up until 3 a.m. watching Howard the Duck—critically assessed as one of history's worst movies—the night before an important morning interview. (To add insult to injury, I still remember the plot of the movie.)

I wasted that time because I misestimated the opportunity cost of watching the movie—that is to say, I didn't accurately weigh the value of everything else I could have been doing instead (like sleeping). If humans were perfectly rational creatures, we would be able to calculate the costs and benefits of every activity well enough to avoid such mistakes, or at least not repeat them over and over. But most people know from their own lives that things don't work out that way. Even experts mess this up: In one experiment on professional economists, nearly 80 percent of the participants failed to correctly estimate opportunity costs.

These errors occur because without prior planning, the impulsive toddler in our heads who has no concept of tomorrow dominates our executive function. That leads us to overestimate the value of a little short-term pleasure and underestimate the value of our long-term well-being. The outcome can be fairly trivial, like playing Angry Birds for 10 more minutes, or more serious, like smoking for one more day—every day.

I only realized how much I hated Howard the Duck when it was over, but we humans also, perplexingly, waste plenty of time doing things we already know we don't want to do. Take the case of the smartphone: It is convenient and helpful as a tool. Yet despite its benefits, in a 2015 survey nearly one in three smartphone owners said it is more of a "leash" than a source of "freedom." This leash has serious consequences: Psychologists have linked excessive smartphone use to "digital addiction," which in turn can lead to loneliness, anxiety, and depression.

So why do millions still submit to the leash? Like any other addiction, heavy smartphone use hooks us by stimulating the brain's reward system. This gives us immediate, but very short-lived, gratification, which quickly wears off and leaves us with regret as we crave yet another hit. Even if it doesn't rise to the level of addiction, any compulsive time wasting that doesn't make us happier in the long run—whether it takes the form of Solitaire or cat videos—can similarly harm our well-being.

For the sake of happiness and productivity, our goal should not be to squeeze every second of distraction and leisure out of our days. Rather, it should be to manage our days in accordance with our priorities, by distinguishing between the time wasters we like and those we don't—and ridding ourselves of the latter. Here are two ways to get started.

1. Schedule your downtime.

The best way to deal with the opportunity-cost problem is not to leave time-use decisions to the moment we begin an activity, when our decision making might be distorted by short-term comfort seeking (especially if it's 1 a.m., when Howard the Duck is likely to air). In his book Deep Work, the writer Cal Newport recommends a productivity strategy called time blocking—making decisions about how to use time in advance, and sticking to the schedule.

Time blocking doesn't have to be limited to work. For many people working from home during the pandemic, job and life have commingled in frustrating ways because there is no exoskeletal time structure imposed by a formal workplace. My answer is to block everything, including hobbies, leisure, and even daydreaming. For example, you might write "Goof off" on your planner from 1:30 to 2 p.m. tomorrow. Since goofing off is no longer an uninvited guest in your schedule, it doesn't throw off your rhythm, and your odds of being back to work at 2 rise dramatically.

2. Give your bad habits a monetary value.

In 2012, two management scholars at the University of Toronto conducted a series of experiments in which they asked participants to think of their incomes in terms of an hourly wage, as well as assign a monetary value to the time they spent on leisure activities. For example, participants were asked to consider their (nonworking) time on the internet in terms of foregone wages. Thinking this way reduced the happiness people derived from their leisure activities.

The researchers interpreted this finding as a negative consequence of monetizing leisure, but such a method can be of great value for dissuading us from engaging in addictive pastimes we dislike. Say, for example, that you find yourself bingeing on social media, which research has clearly found lowers happiness when overused, especially for young people. If you consume the average amount of social media in America (about 142 minutes per day) and earn the average hourly wage (about $29.92), you are effectively "spending" about $71 worth of time per day on this activity.

Remember your hourly wage at the beginning of each day, and get in the habit of reminding yourself of it as you start something that might ordinarily gobble up your time. You'll be more likely to make a cost-effective decision to use social media to quickly catch up on your friends' lives and the news, and not to feed your brain's reward system through a costly hour of mindless scrolling.

There is a particularly winsome passage in Walden in which Thoreau compares time to a stream. "Time is but the stream I go a-fishing in," he writes. "I drink at it; but while I drink I see the sandy bottom and detect how shallow it is. Its thin current slides away, but eternity remains." To fish in the river of time—even without catching anything—is no waste. It can be a special kind of reverie.

The problem is if you fish when you should be hunting, or fly-fish if you prefer bait casting. And so it is with any pastime—even reading Walden, I realized. It is a lovely book, full of insight. But at a certain point, one has to put the book down and get back to work.

Arthur C. Brooks is a contributing writer at The Atlantic, the William Henry Bloomberg professor of the practice of public leadership at the Harvard Kennedy School, a professor of management practice at the Harvard Business School, and host of the podcast The Art of Happiness With Arthur Brooks.