Ah, sleep. Why is our most precious recharging resource so scarce in our busy, modern lives?

We all know the excuses: demanding schedules, social lives and screen time. Sometimes it's subconscious, but we're all making decisions to do these things instead of getting the sleep we need.

ABC News Chief Medical Correspondent Dr. Jennifer Ashton walked us through some of the most common myths about sleep to set the record straight.

Myth 1: I can function just fine on 5 to 6 hours of sleep, so I don't need to change my habits

FALSE: 95% of adults need 7 to 9 hours of sleep a night.

Getting enough sleep, is a "massive problem in this country," according Ashton.

"Sleep has a PR problem. I think we look at sleep like it's a luxury, but it's actually a medical necessity," she said. "Just because you can function on less sleep doesn't mean you should function on less sleep."

Myth 2: If I don't get enough sleep during the week, I can make it up over weekend

FALSE: "Our body's circadian rhythms are finely tuned and connected to regular sleep behavior. And our hormones, our metabolism, all kinds of neurotransmitters, are all tied into those circadian rhythms and when we're sleeping," Ashton said.

Weekend schedules often vary from our weekdays, but it's best to not alter your sleep schedule by more than an hour on either end.

"Locking down a sleep schedule is not just important for infants and babies; it's really important for adults as well," Ashton said.

Myth 3: I might be tired the next day, but there are no long-term effects of not getting enough sleep

FALSE: "People who consistently get insufficient sleep are at increased risk for neurocognitive decline, dementia, poor concentration, mood disorders like depression and anxiety -- and that's just from the neck up," Ashton said.

Poor sleep affects our ability to efficiently metabolize food, and puts us at increased risk for cardiovascular disease and cancer, Ashton added.

Myth 4: It's OK and faster to fall asleep with the TV on

FALSE: "Don't fall asleep with the TV on," Ashton said. "You might think you're asleep, but your brain is registering that light, and it's actually stimulating your brain and helping to prevent good, quality sleep."

On that note, any light that's visible to you -- even a street lamp in the distance or a hall light under the door -- is affecting your sleep. Blackout curtains are your best friend.

Myth 5: You get better sleep when your bedroom is cold

TRUE: If you often get up the middle of the night, it might be your body waking you up because you're sweating or too hot.

Ashton keeps her room at a cool 66 degrees year-round for a restful and undisturbed night of sleep, but you can adjust your levels to whatever feels comfortable for you.

Myth 6: Bedtime starts when you get in bed

FALSE: You should unplug an hour before you want to go to bed. Put your phone down, turn off the TV and get off the computer. Even dimming the lights in your house will signal to your brain that it's time to go to sleep.

Treat yourself to a warm bath or shower, drink chamomile tea or read a good book.

Then by the time you get into your bed, "Your brain should say I'm here to sleep," Ashton said.

Myth 7: Getting exercise during the day will help you get better sleep

TRUE: If you exercise for 30 to 60 minutes during the day, you'll be more tired by the time you get into bed.

Ashton also recommends meditation at some point in the day as another way to ensure you fall asleep more easily.

Myth 8: It's OK to use sleeping pills

FALSE: "I can't emphasize this enough -- there are no prescription sleeping pills that are approved for long-term use," Ashton said.

While they can be safe and effective in the short term, they affect your brain chemistry and are harmful to use long term.

Myth 9: You can't get too much sleep

FALSE: Too little or too much sleep is bad for you.

"Too much sleep sends different messages to our body ... maybe we're sick, maybe we're injured," Ashton said.

"It disrupts our circadian rhythms, our metabolisms. Don't be lured into this false sense of security that more is better -- when it comes to sleep, that's not true," she added.

Myth 10: Naps disrupt your sleep

FALSE: Nappers, rejoice! A quick, 20-minute power nap can help your body recharge and won't impact your sleep.

For all of us who often find ourselves taking non-optional naps during the day, remember: A nap longer than an hour is too much, and you can't nap in lieu of getting the full seven to nine hours you need.

"When you hear the recommendation of seven to nine hours a night," Ashton said, "that refers to continuous sleep."