As it turns out, scientists have been looking for answers to these questions too.
You can use their answers to guide many of the decisions you make on a day-to-day basis, from what you eat in the morning to how often you wash the sheets you sleep in.
If you showered yesterday, you should probably skip it today. A growing body of evidence suggests that showering too much can mess with your skin and dry out your hair. That's because in addition to sloughing off dirt and pollutants, you're also showering away many of the naturally occurring but beneficial bacteria and oil that keep skin and hair healthy.
"It's paradoxical, but people who wash their hair a lot to get rid of oil are drying out their scalp and producing more oil," Lynne Goldberg, a dermatologist and the director of Boston Medical Center's hair clinic, told Business Insider.
When it comes to setting up your own regimen, you should consider two things: the average dryness of your skin and scalp and the texture of your hair. If they are neither very oily nor very dry, you likely only need to bathe once or twice a week. If your hair is curly and thick, you may need to wash it even less frequently, since coarse hair slows down the spread of oil from your roots through the length of your hair.
Brew your coffee -- but don't drink it yet.
Many things naturally happen to our bodies when we wake up. In addition to developing a magical ability to ignore loud noises like an alarm, our bodies also start pumping out the hormone cortisol, a sort of natural caffeine. Most people's cortisol levels peak sometime between 8:00 and 9:00 in the morning.
Instead of hopping aboard this wakefulness train, however, coffee consumed at this time may actually blunt cortisol's natural effects, according to Stephen Miller, a Ph.D. candidate at the Uniformed Services University of the Health Sciences in Bethesda, Maryland. Instead of caffeinating during this window, Miller recommends holding off for an hour after you awaken.
Hit the track.
Research suggests that an early-morning workout on an empty stomach helps speed weight loss and boost energy levels by priming the body for an all-day fat burn. Exercising first thing in the morning may push the body to tap into its fat reserves for fuel instead of simply "burning off" the most recent snack or meal.
Plus, working out early could mean you get more sunlight, which is key to properly setting your body's internal circadian rhythm. In one study, people who basked in bright sunlight within two hours after waking were thinner and better able to manage their weight than those who didn't get any natural light, regardless of what they ate throughout the day.
Get your heart pumping.
Any kind of exercise is a healthy way to start the day, but the type that will have the most benefits for your body and brain is aerobic exercise, or cardio.
"Aerobic exercise is the key for your head, just as it is for your heart," write the authors of an article in a Harvard Medical School blog called Mind and Mood.
Cardio is the closest thing to a miracle drug that we have. Studies suggest that running or swimming helps to lift mood, clear the mind, and may even help protect from some of the cognitive decline that occurs with age. It also strengthens the heart and lungs and helps tone up muscles. So get moving -- preferably for at least 45 minutes at a time.
If you normally eat breakfast, there are three key ingredients it should have: protein, fiber, and healthy fats. Most US breakfasts are lacking in all three. Instead, they're full of refined carbs, a type of unhealthy carbohydrate that gets rapidly turned into sugar in our bodies. Pancakes, bagels, muffins, and even cereal all fall into this category. Add juice to the mix and you've got a big dessert.
Instead, try a couple of eggs with a few avocado slices or some Greek yogurt (not regular, as it can be high in sugar) and nuts. Both of these options will fill you up, help smooth out your digestion, and power up your muscles.
Or skip breakfast entirely.
If you're looking to lose weight and other diets have failed you, you might want to try an eating plan known as intermittent fasting -- after checking in with your doctor, of course. There are several versions of the diet, but one of the most popular involves fasting for 16 hours and eating for eight. Most people opt for an eating window of 12 p.m. to 8 p.m , meaning you essentially skip breakfast but eat whatever you want within the eight-hour "feeding" window.
Large studies have found intermittent fasting to be just as reliable for weight loss as traditional diets. And a few studies in animals suggest it could have other benefits, such as reducing the risk for certain cancers and even prolonging life -- but those studies need to be repeated in humans.
Ditch the multivitamin.
The ingredients you're looking to get from a multivitamin are better processed by your body when they come from real food. If you're not eating right, taking a vitamin isn't going to do you much good anyway. These are among the reasons that experts suggest people stop taking many vitamins and supplements, which make up a largely unregulated industry.
"Consumers should expect nothing from [supplements] because we don't have any clear evidence that they're beneficial," S. Bryn Austin, a professor of behavioral sciences at the Harvard T.H. Chan School of Public Health, told Business Insider. "They should be leery that they could be putting themselves at risk."
Thousands of Americans work in jobs that afford them the privilege of sitting for the majority of the day. If you're one of them, you probably also know that being on your rear all day also comes with some health concerns, including sore muscles, strained eyes, poor circulation, and weight gain.
To avoid these issues, it's important to have proper posture. To find yours, try this simple exercise: Sit at the end of your chair and let yourself slouch. Now, try to sit up straight, accentuating the curve of your back as much as possible. Hold this position for a few seconds. Next, release the position a little bit -- no more than about 10 degrees. This is your proper sitting position.
Get up and move around every hour.
Even if you're sitting properly, you should be up and about at least once every hour. That's based on a set of guidelines compiled by an international group of scientists in 2015and an observational study of close to 4,000 American adults, which found that people who ambled around for about two minutes every hour had a roughly 33% lower risk of dying prematurely than those who sat all day.
Drink plenty of water.
Staying hydrated is vital. Our bodies are 60% water, and not getting enough can lead to headaches, fatigue, and even overeating. Still, contrary to popular opinion, you don't necessarily need to drink eight glasses of water a day.
Instead, your daily hydration requirementcan change based on several factors, from how much you worked out that day to the weather outside. Certain foods are also a good water source, so eating more of them may mean you need to drink less. Cauliflower, eggplant, peppers, and spinach are all 92% water. Carrots, green peas, and even white potatoes are more than 79%.
Have a lunch that looks somewhat like your breakfast.
Just like your morning meal, your lunch should fuel you up, not slow you down. Avoid carb-heavy meals that are high in sugar and low in protein, like pizza, premade sandwiches, and fried foods. Instead, opt for meals rich in protein, fiber, whole grains, and healthy fats.
Foods like eggs, lean meat, beans, and chickpeas are high in the first ingredient; brown rice or quinoa is a good source of the third; salmon, avocado, and olive oil are all rich in the last ingredient.
Take breaks from screens to avoid eyestrain.
Are your eyes dry, itchy, blurry, or irritated? You may be suffering from what ophthalmologists call "digital eyestrain." To avoid it, make sure you're drinking (and blinking) enough and set your computer up in a way that minimizes glare. You can also practice what's known as the 20-20-20 rule.
Every 20 minutes, look at something at least 20 feet away for 20 seconds. This will allow your eyes to rest, Rahul Khurana, the clinical spokesman for the American Academy of Ophthalmologists told my colleague Kevin Loria.
Watch your mid-afternoon caffeine intake.
The Mayo Clinic advises adults to limit their caffeine intake to 400 mg per day, or the equivalent of about two to three coffees. That caffeine content can differ dramaticallybased on the type of coffee, however. Just 1.5 cups of Starbucks, for example, gives you 400 mg of caffeine, while you'd need four cups of McDonald's drip coffee to equal that amount.
Like too much of anything, too much caffeine comes with risks, including migraine headaches, irritability, upset stomach, and even muscle tremors -- so it's important to know how much you're getting.
Snack on something you've prepped ahead.
For a mid-afternoon energy boost, avoid the vending machine and opt for a healthy homemade snack. Sliced apples, nuts, carrots with hummus, Greek yogurt, and celery with peanut butter all make great go-to snacks.
"We live in a society where making healthy choices ... it's not defaulted toward that," registered dietitian Andy Bellatti told Business Insider. "Unhealthy foods are cheaper and they're everywhere; if you go to any store, you can buy a candy bar at the checkout but not a piece of fruit."
The best way to ensure you'll eat something nutritious is to bring it yourself.
On your commute home, don't agonize over germs.
A team of geneticists made headlines in 2015 for a mission to document all the bacteria on the New York City subway. They turned up nearly 600 different species of microbes crawling around on all those greasy rails.
Before whipping out the hand sanitizer and tissues, keep this in mind: Almost all of the germs they found were completely harmless. In fact, there's evidence to suggest that regular exposure to germs helps keep our immune systems healthy by priming it to more easily recognize dangerous microbes in the future. The idea could partially explain why children who grow up around animals and in rural areas are less likely to develop conditions like asthma than children who don't.
Skip happy hour, or go simply for the food and company.
Alcohol is one of the world's most widely consumed drugs, but drinking even small amounts -- as little as one glass of wine or beer a day -- has been linked with a host of negative side effects, including cancer. In November, the American Society of Clinical Oncology, a group of the nation's top cancer doctors, released an unprecedented warning in which it told Americans to drink less.
"ASCO believes that a proactive stance by the Society to minimize excessive exposure to alcohol has important implications for cancer prevention," the statement said.
So at your next happy-hour event, consider skipping the booze or doing something else.
If you go out for dinner, plan on taking a third of it home.
The average size of many of our foods -- whether fast food, sit-down meals, or even items from the grocery store -- has grown by as much as 138% since the 1970s, according to data from the American Journal of Public Health, the Journal of Nutrition, and the Journal of the American Medical Association. So be mindful of portion sizes, and if you're eating out, consider taking anywhere from a third to half of it to go.
Put away screens for at least 30 minutes before bedtime.
The blue light that illuminates our screens also tamps down on the production of melatonin, a key hormone our brains use to tell our bodies to start preparing for sleep. That's something you don't want to be doing at night, especially right when you're heading to bed. Experts recommend at least 30 minutes of no-screen time before bedtime.
Before you tuck in for the night, make sure your sheets are clean.
Our beds can blossom into a "botanical park" of bacteria and fungus within as little as a week, New York University microbiologist Philip Tierno told Business Insider.
The combination of sweat, animal dander, pollen, soil, lint, dust-mite debris, and plenty of other things is enough to make anyone sick, let alone someone with allergies. So clean your sheets at least once every seven days.
This post originally appeared on Business Insider.