You know that drinking too much can mean a bad night’s sleep, but just one glass of wine or a nip of bourbon before bed won’t hurt you, will it?

It will. You may fall asleep fine, but as little as one drink can impair sleep quality. The alcohol can interfere with the deep, restful stage of sleep that lets you wake up feeling rejuvenated, according to sleep expert Michael J. Breus, PhD.

The idea that one drink at bedtime is harmless is just one of the sleep “myths” that might be robbing you of quality sleep—and therefore reducing your energy and mental focus, too. (If you don’t wake thoroughly refreshed on most mornings, here’s what Dr. Breus suggests—for each alcoholic drink you consume on a given day, stop drinking at least that many hours before bed.)

Here are eight more sleep myths that Dr. Breus regularly encounters and that might be harming your sleep…

Myth: Thomas Edison, Leonardo da Vinci and Mozart excelled on only a few hours of sleep, so I can, too?

Truth: Some people, maybe including those above, have a rare genetic abnormality that lets them do well on little sleep. If you had that anomaly, you would know it—you would wake every morning feeling refreshed after perhaps three to five hours of sleep.

What to do: When your schedule permits—for example, during a ­vacation—let yourself fall asleep at whatever time you feel tired in the evening and rise whenever you awake refreshed. Don’t set an alarm. Do this for a week or more. The amount of sleep you get on these nights likely is the amount that your body needs—for most people, that will be between six-and-a-half and eight hours.

Myth: People require less sleep as they age. 

Truth: We do tend to sleep less deeply and wake up sooner as we age—but that’s because we have more trouble sleeping. The result can be less alertness and focus and unintentional “napping” while watching TV or reading.

What to do: If you can’t get sufficient sleep at night, schedule early-afternoon naps to avoid poorly timed unplanned naps or loss of mental sharpness.

Myth: I don’t sleep at all some nights! 

Truth: People sometimes imagine that they have lain in bed all night without getting a wink of sleep—but they’re usually wrong. Most likely, you drifted off at least once or twice but woke up within a few hours each time. People who wake during the early stages of sleep often believe that they never fell asleep at all.

What to do: If you want to find out how much you really are sleeping—and perhaps, reassure yourself—wear a sleep-­tracking device to bed. Most wearable fitness trackers include a sleep-tracking function. (Note: If you find that after using a tracker you sleep fewer than five hours in total over 24 hours, wake up for more than 30 seconds more than twice an hour and wake up feeling unrefreshed, you should see a sleep specialist about possible clinical insomnia.)

Myth: Sleeping in on the weekends can help me live longer. 

That’s how a lot of news articles covered a new study published in Journal of Sleep Research. It’s technically true—but only compared with people who always sleep five hours or less a night on weeknights. They were helped by sleeping in on weekends.

Truth: Unless you get very little sleep throughout the week, regularly oversleeping on weekends is bad for your health. The truth is, you can’t entirely “make up” for sleep lost during the week—research shows that you’ll still have worse reaction time (behind the driver’s wheel, for example) and mental focus. Plus, too much weekend sleep can throw off your sleep/wake schedule so that it’s hard to fall asleep early enough on Sunday night—messing up another week’s schedule. That’s called “social jet lag.” In fact, studies find that a pattern of sleeping more than two extra hours on weekends is linked to a rise in blood fats (triglycerides), increased risk for diabetes, weight gain and depressed mood. Sleeping in up to an hour or so on a Saturday or Sunday, though, is fine.

Myth: When I can’t fall asleep, the best thing I can do is stay in bed. 

Truth: Chances are you’ll get ­frustrated—which makes it even harder to fall asleep.

What to do: If you’ve been lying in bed for 25 minutes or longer and you sense your frustration rising, get out of bed and do something you find relaxing until you feel sleepy, such as reading a book or magazine (not your smartphone or tablet) in a chair. Exception: If you feel relaxed, not frustrated, continue lying there until you drift off.

Myth: Counting sheep is a time-tested strategy for falling asleep. 

Truth: It’s time to put the sheep back in the barn—counting them won’t reduce the time you need to fall asleep, according to research at Oxford University. Counting sheep (or counting anything else you might imagine instead) requires so little brainpower that you still can ruminate about the other matters that are probably keeping you awake.

What to do: Engaging your brain as a distraction can help you fall asleep ­faster, but it needs to be something more involving. Example: Try counting backward by threes starting at 300. That’s boring enough to promote drowsiness but requires sufficient brainpower to deter your mind from wandering to other matters.

Myth: A warm, cozy bedroom is conducive to sleep. 

Truth: When the body is warm, it produces less melatonin, a hormone that helps us enter the sleep cycle. Exception: There is some evidence that keeping the feet warm—wearing socks, for ­instance—can encourage sleepiness.

What to do: Set your bedroom temperature to between 65°F and 75°F at night. The optimal temperature for most people is 68°F to 72°F. When you have trouble falling asleep, try lowering it a few degrees at a time to see whether that helps.

Myth: A glass of warm milk will help me fall asleep. 

Milk contains tryptophan, an amino acid that can be conducive to sleep—but you would have to drink a gallon and a half of milk to have any significant sleep benefit from the tryptophan. People may feel sleepy when they drink warm milk because they associate the beverage with comforting memories of a loved one putting them to bed in childhood.

What to do: If drinking warm milk helps you fall asleep, go ahead and drink warm milk—the sleep benefits are purely psychological, but that doesn’t mean they’re not real. The good news is that if you’re lactose-intolerant, warm soy milk or almond milk should work just as well—it’s the feeling of comfort, not the milk itself, that matters.