If you’re always tired, you’re not alone. 

Forty percent of adults say fatigue interferes with their daily activities at least three days a week, according to the National Sleep Foundation.

So, why are so many people tired during the day?

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Fox News Digital spoke with several sleep experts about common reasons for daytime sleepiness — and how to ensure the right amount of rest for mental and physical wellness.

Check out these four issues. 

1. Poor sleep habits

While constantly feeling tired can be linked to many factors, it all starts with getting the right sleep.

That’s according to Tim Roberts, VP of science and innovation at Therabody, a Texas-based wellness technology company.

“The first thing to evaluate when building improved and healthy sleep habits should be your sleep schedule,” he told Fox News Digital.

Evaluate whether you can actually get seven to eight hours — and if there is a consistent sleep schedule in which you go to bed and wake up at similar times all week long.

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Next, assess whether you’ve created a sleep environment that is conducive to helping you sleep better. “Think cool, dark, quiet and comfortable,” said Roberts. 

2. Stress-triggered restlessness

Many people have trouble falling asleep and then wake up frequently during the night, causing them to feel tired during the day, said Dr. Kathrin Hamm, sleep expert and founder of Bearaby, a New York City sleep and wellness company.

“The root cause of nighttime restlessness for many people seems to be related to anxiety or stress,” she told Fox News Digital. 

“It’s not uncommon for the human nervous system to need sensory support to destress, to be able to naturally shift from sympathetic (fight or flight) to parasympathetic (rest and digest),” she went on. 

“When our bodies struggle to make this nervous system shift, it often affects sleep quality.”

3. Vitamin deficiency

Constant fatigue can sometimes be caused by a deficiency in essential nutrients crucial for optimal energy production, according to Grant Antoine, a naturopathic doctor and clinical expert at Viome, a Washington-based biochemistry company focused on diet and lifestyle. 

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“Leaping toward supplements like B vitamins, Coenzyme Q10 or NAD precursors without a thorough understanding could be counterproductive,” he said. 

Antoine recommends taking a personalized approach to supplements, starting with a comprehensive assessment to ensure that you’re getting the right mix of nutrients for your individual biochemistry and energy needs.

4. Blue light at night

The use of technology before bed can contribute to a poor sleeping environment, experts agree.

“Some technologies, particularly those with screens that emit blue light, can be detrimental to your sleep, but more recently, technologies that can help calm the mind and relax areas of tension in the body have been shown to improve sleep quality when used as part of the bedtime routine,” Roberts said. 

“The root cause of nighttime restlessness for many people seems to be related to anxiety or stress.”

“By focusing on these things, it is possible to improve sleep quality, alleviate persistent tiredness and enhance overall well-being,” he added.

Hamm agreed that blue light is a common culprit.

“Light impacts our sleep/wake rhythms greatly, so if you’re surrounded by blue light from your devices right up until you try to sleep, you may have a difficult time drifting off,” she told Fox News Digital. 

“Good sleep hygiene is all about syncing up with your body’s natural rhythms.”

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Above all, the key to quality sleep is to find the methods, environments and positions that are best for you, experts said. 

“Sleep health is highly personalized. Some of us are side sleepers, some of us are stomach sleepers,” Hamm said. 

“Some people prefer to sleep ‘cozy,’ while others prefer cool and breathable bedding. The key is to figure out what your personal preferences are, and from there curate a consistent bedtime routine.”

Common sleep hygiene practices that benefit most people are to rest in a dark environment by using a sleep mask or black-out curtains, and to maintain a consistent bedtime and wake-up time, Hamm said.

“If your fatigue seems to last all day, it’s always best to visit a health care professional to help determine whether there might be an underlying medical condition requiring attention,” she added.

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