If you have kids or you were once a child (so, all of us) you probably recognise the signs of overtiredness straight away - cranky, hyper, and overemotional.
But can you recognise them in yourself?
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In her new book The Little Book of Sleep, US sleep psychologist Dr Nerina Ramlakhan says overtiredness is becoming more common, and is leading to insomnia for many adults. In fact, Dr Ramlakhan told the Guardian she's getting more clients who remind her of her own young daughter - and that's because we're over stimulated.
The main problem according to Dr Ramlakhan is that when many of us are queuing at the supermarket or streaming television series without ad breaks, we have no time to daydream or relax.
"We have become restless as a society... We have lost the rituals and practices that gave us little respites during the day," she says.
Dr Ramlakhan said our inability to shut off means we're often lying just on the edge of sleep.
"People say to me they're getting up in the morning feeling exhausted. They say they keep waking up at night and can't get back to sleep. But it's normal to wake up at night; most of the time, we just go back to sleep."
What are the signs that you may be overtired? If you get into bed at night and find your mind is still racing with what has been going on through the day, overtiredness could be to blame. During the day, you might be irritable, unfocused, and reaching for sugary snacks (guilty).
So how can you learn to shut off?
You've probably heard it before but having a relaxing pre-sleep routine is important.
"Our body craves routine and likes to know what's coming," Dr Epstein, co-author of The Harvard Medical School Guide to a Good Night's Sleep told Psych Central. By creating a pre-sleep ritual, you're establishing a clear association between certain activities and sleep. This might be reading, or taking a warm bath.
Dr Epstein also suggests listening to calming music, stretching or doing relaxation exercises, including progressive muscle relaxation (going through each muscle group and tensing and relaxing it) and deep breathing.