🔕↗
When your phone buzzes, even if you don't look at it or touch it, your score on attention tasks drops. The drop is about the same as when you actually take a call or send a text. There is another case: if the phone is just sitting on the desk and you resist looking at it, the mental capacity you have free still shrinks. The more dependent you are on your phone, the bigger the drop.
- High value
- Evidence B
- Saves time
⏰↗
The one-fifth of people with the most irregular schedules had body clocks about 2.5 hours later than the one-fifth with the most regular ones. That is like living in jet lag all the time. Students with more regular schedules also had better grades.
- Moderate value
- Evidence B
- Saves time
🛌↗
After two weeks of only 6 hours of sleep a night, your mental performance drops to about the level of going two days and nights without sleep. The trouble is that you can't feel it. Self-rated sleepiness stops rising after the first few days, and people sleeping 6 hours rate themselves as sleepy as people sleeping 4. So “6 hours is enough for me” is itself a symptom of not sleeping enough.
- Moderate value
- Evidence A
- Saves time
☕↗
Taking 400 mg of caffeine 6 hours before bed, about three or four cups of coffee, cost people more than 1 hour of sleep that night as measured by instruments. Yet their own sleep diaries showed no difference at all. One 250 mL cup of coffee (107 mg) has to be finished more than 8.8 hours before bed so that it doesn't affect sleep. If you go to bed at 11 p.m., 2 p.m. is the line.
- High value
- Evidence A
- Saves time
📥↗
The same group of people were compared over two weeks. In the week when email checks were limited to 3 times a day, daily stress was clearly lower, while the number of emails sent and received was the same. With no limit, people checked an average of 15.5 times a day.
- Moderate value
- Evidence B
- Saves time
🚪↗
One interruption averaging 2.8 seconds doubles the chance of making an error in the steps that follow. A 4.4-second interruption triples it. A field study also found that it takes an average of 25 minutes to get back to the interrupted task, with two other things squeezed in between. Interrupted people worked faster, but their stress, frustration and effort were all higher.
- Top value
- Evidence B
- Saves time
🎯↗
When you switch tasks, you react more slowly and make more mistakes. People who often have several screens going at once have not trained themselves to do several things at once; they actually do worse on task-switching tests.
- Moderate value
- Evidence B
- Saves time
📵↗
Reading on a glowing screen before bed means falling asleep about 10 minutes later than reading a paper book. Melatonin is suppressed by 55%. The next day the body clock is pushed back by more than 1.5 hours, so you are sleepier in the morning and take longer to wake up fully.
- Moderate value
- Evidence B
- Saves time
🛏️↗
In 2025, people in China slept an average of 6.97 hours a night and fell asleep at 0:10 on average. People who use a phone or tablet before bed have more than twice the chance of not getting enough sleep, and 2.7 times the chance of daytime drowsiness. If the device is merely kept in the bedroom unused, the numbers are about the same. So the easiest approach is to keep the phone out of the bedroom.
- High value
- Evidence B
- Saves time
- Disputed
🌙↗
When people are well rested, they quickly learn to avoid high-risk options. After two nights without sleep, they instead keep choosing high-risk ones, and the effect is stronger the older the person. How much a few hours of lost sleep matters has not been measured, but it is still better to put important decisions off until after you have slept.
- Moderate value
- Evidence B
- Saves time
💤↗
A 10-minute nap perks you up on the spot, and the effect lasts two and a half hours. A 5-minute nap does almost nothing. A 20-minute nap takes half an hour to start working. After a 30-minute nap, you wake up in a fog for a while, and in that period you perform worse than if you hadn't slept.
- High value
- Evidence B
- Saves time
🎧↗
When background noise rose from 39 decibels to 51 decibels, people remembered fewer words, got more tired and felt less like working. During breaks, watching a nature film with sound restored energy better than continuing to listen to office noise.
- Moderate value
- Evidence B
- Saves time
⏱️↗
Records from British munitions factories in World War I show that up to 49 hours a week, output rose with hours worked. Beyond 49 hours, each extra hour added less and less. Working 70 hours a week produced almost the same as working 56, so the extra 14 hours were wasted.
- High value
- Evidence B
- Saves time
🧠↗
Replaying the same upsetting thing will not produce an answer. It only deepens depression, nails the negative thoughts in more firmly, makes you worse at solving problems and less able to act, and wears out the people around you who are willing to listen. When you notice you are going in circles, go do something that takes your hands.
- Moderate value
- Evidence B
- Saves time
🩺↗
In a 20-year twin study, each step up in pessimism was linked to about a 13% higher chance of dying over the same period, and about a 20% higher chance of dying of cardiovascular disease. In the other direction, a high optimism score did not bring a matching benefit. So what needs handling is pessimism, not a lack of “positive energy.”
- Moderate value
- Evidence B
- Buys life
- Disputed
🤝↗
The damage done by one person who drains you is greater, and more consistent, than the benefit from one person who supports you. So subtract first, then add.
- Moderate value
- Evidence C
- Saves time
🚶↗
Looking at what just happened from a different angle, or putting yourself in the other person's position, can both bring the emotion down, and the latter works better. Just not showing the emotion also helps a little; forcing down the feeling inside or forcing yourself not to think about it does nothing. People who punished an offender ended up replaying the incident for longer afterward, while people who did not retaliate moved on faster.
- Moderate value
- Evidence B
- Saves time
🫶↗
For depression, brisk walking and jogging work best, and the harder the exercise the more effective it is; for details see §22.6 (if you feel bad, go for a walk or a run). Light exposure is very effective for seasonal depression, and also works for depression that is not seasonal. Online self-help cognitive behavioral courses work, and when symptoms are more severe it is better to do them with someone guiding you. If you can't cope, call 12356 (China's national mental-health hotline) first.
- High value
- Evidence A
- Saves time
📋↗
Police officers, doctors and bank tellers are people working by the rules of their posts, bound by paperwork, deadlines and oversight. Whether their attitude is good has little to do with whether your matter gets handled or how many days it takes. So get a receipt, note the deadline and use the appeal channel, and don't try to argue until the other side agrees.
- Moderate value
- Evidence C
- Saves time
🪞↗
People who habitually compare themselves online with people who are doing better tend to have worse moods and lower self-esteem. People who deactivated Facebook for four weeks had a small increase in well-being, but also knew somewhat less about current events. People who limited each of three social platforms to 10 minutes a day had lower loneliness and depression after three weeks.
- High value
- Evidence A
- Saves time
👀↗
People who walked into a room wearing an embarrassing T-shirt thought nearly half the people there could recognize who was printed on it; in fact it was under a quarter. People overestimate the same way when the T-shirt is a flattering one. After a group discussion, people also think others remember their mistakes more clearly than they do. After a conversation, people also commonly underestimate how much the other person likes them. So when you feel that “everyone remembers me embarrassing myself,” cutting it in half is still too high.
- Moderate value
- Evidence B
- Saves time
🧩↗
People who always feel that “the people around me demand perfection, and if I can't deliver I'll be rejected” are more likely to have thoughts of suicide. The link for “I demand perfection of myself” is much weaker, only about a third of the first. Even after removing the thoughts people already had, the first feeling is still linked to more such thoughts later, though only modestly.
- Moderate value
- Evidence B
- Buys life
🌬️↗
Venting methods that rev the body up, such as hitting a punching bag, throwing things or going for a run, do not take away anger overall. Methods that calm the body, such as slow breathing, mindfulness and meditation, clearly lower anger and the urge to lash out.
- Moderate value
- Evidence A
- Saves time
✍️↗
Writing down an upsetting thing has a benefit on average, but a very small one. The pooled conclusions are also inconsistent: two pooled analyses found no effect. It costs almost nothing, so you can try it. If your emotional problems are serious, don't use it in place of seeing a doctor.
- Moderate value
- Evidence B
- Saves time
- Disputed
🩹↗
For period pain, taking a drug such as ibuprofen raises the share of people whose pain clearly eases from under two in ten to about half. It works better than acetaminophen, with somewhat more side effects. If the pain keeps you from work or school, hurts deep inside during sex, or isn't controlled after three months of medicine, see a gynecologist to be checked for endometriosis. On average this disease goes 6.7 years before it is diagnosed.
- Moderate value
- Evidence A
- Saves time
- For: Women
