There's nothing more annoying than being awake in the middle of the night, feeling desperately tired, but not being able to fall back to sleep. (On second thought, add extra annoyance points if your partner is slumbering peacefully next to you, and even more if they're snoring.)
But seriously, who else has ever hit the hay at 10pm and fallen asleep without an issue, only to wake six hours later, tired and wired?
"It's a common question, and I think the first thing is to realise we do wake up regularly during the night because we sleep in cycles," Dr Dev Banerjee, sleep specialist at Integrated Sleep Health tells HuffPost Australia.
"The cycles are generally about 90 minutes to two hours, though I think we tend to cycle more as we get older, and aren't able to sustain that deep sleep as much as we used to.
"But mostly when we wake up after a cycle, we will roll over or shuffle or maybe have a sip of water and then go back to sleep again. So we actually wake up several times a night.
"When people come to me and say, 'I wake up a lot in the middle of the night and can't go back to sleep,' I tell them it's not the waking up that's the problem, it's the getting back to sleep."
But why is it so easy to fall asleep initially, yet so hard at 3am?
"Think of sleep and wake as a yin and yang type relationship," Banerjee says. "If you go to bed at night, you immediately start to catch up on the sleep debt you have accrued over the last 16 hours or so.
"By the time you wake at 4am, you have repaid some of that sleep debt. So it tends to be harder for people to fall asleep at that time, even though you still need those last couple of hours."
"Stress can be a contributing factor to that 'tired and wired' feeling you mentioned before," Banerjee says.
"Even if you go to bed exhausted, the brain remains very busy. So you might be exhausted but after a cycle or two, you still have that 'fight or flight' response going on. I see this a lot in anxious, stressed people who are busy in their lives. They can initially fall asleep fine but once they are awake in the middle of the night, they can't get back to sleep again, because the brain is hyper alert and a bit more awake."
"A small amount of alcohol is quite nice to relax, I'll be honest, but if you drink a little bit too much it tends to fragment sleep a lot more," Banerjee says.
"And that has to do with how it reacts with neuron chemicals in the brain.
"There is no doubt heavy drinkers have fragmented sleep, and if your sleep is fragmented you are likely to wake more.
"Let's not forget too much alcohol is a lot of bladder filling as well which obviously affects sleep and disturbs sleep."
"Early morning wakening with an inability to get back to sleep is actually quite a common sign of depression. Those who have depression tend to have a lot of early morning wakings.
"If someone comes to me and says 'I regularly wake up at four and can't get back to sleep', I tend to think outside the box and think, 'is it a bit of a mood disturbance?'"
To find out more about the link between depression and sleep, head here.
Tips and tricks
Preparation for a good night's sleep doesn't start in the middle of the night when you're wide awake and staring at the ceiling.
"If you go to bed highly strung, tense, and just flop into sleep, it's a recipe for disaster later on" Banerjee says. "You want to wind down and get everything in order.
"Don't take your phone to bed with you, make lists to get all the thoughts off your mind before you go to sleep -- all that simple common sense stuff we do for sleep hygiene -- all if it is important and a lot of it has to be done before you actually head to bed."
Count sheep (yes, really)
Except they don't have to be sheep.
Says Banerjee: "I don't know why sheep. Is it a New Zealand thing? I don't know how that came to be so popular. In Beijing it would be people wouldn't it? Why wouldn't you count people?
"Seriously though, I think it's more of a distractional therapy to calm those thoughts pumping out of their head. They're always really silly thoughts, the things that keep you up, things like 'I've run out of potatoes' or 'I think it's going to rain tomorrow'.
"It's real nonsense and you are alert and awake thinking about it. Once that happens, ping! The whole brain fires up like a firework display. So anything that can distract you from those thoughts -- sheep or whatever else -- is worthwhile."
The brain is a sly beast and it will play tricks on you. Actively trying to force yourself to go to sleep can backfire spectacularly.Dr Dev Banerjee
Don't force it
"Some people try too hard to get back to sleep. Falling asleep should be effortless," Banerjee says.
"This guy I saw, I said to him, 'what do you do to fall back asleep?' And he said, 'I say to myself: I must fall asleep, I must fall asleep, I must fall asleep.'
"And in actual fact, the result he was getting was the opposite. So I suggested he say to himself 'I must stay awake, I must stay awake, I must stay awake', and he tried it and it actually worked.
"The brain is a sly beast and it will play tricks on you. Actively trying to force yourself to go to sleep can backfire spectacularly."
Watching television or a movie
Playing on your phone or tablet
Get out of bed
According to Banerjee, what seems counterproductive actually might be the secret to your waking woes.
"Some people try and gets out of the bedroom, as if the bedroom becomes a place of poor sleep, the brain will associate the bedroom with poor sleep going forward," he says. "It's called controlled stimulus memory.
"So one idea is to get out of bed and meditate, or else read something utterly boring, like how to treat mould in your microwave. What you don't want to do is put a movie on and the next thing you know, there you are, two hours later still watching.
"It also fascinates me that people get up and have a cup of tea. It has caffeine in it -- what's the point of that? Some people swear by a glass of warm milk but I tend to think having liquid in the middle of the night will make you want to pee later on.
"Another thing people do is get up and snack. That's not healthy. Do it regularly, and you run a real risk of putting on weight."
Don't know how to meditate? Give this one a go.
Consult a sleep doctor
"Certainly, there are instances where fragmented sleep is a short-term situation, such as if you have a cough or cold or know you are going through a particularly stressful time at work," Banerjee says.
"In this case, I suppose you could look at a short-term solution such as sleeping medication if you were really desperate.
"But if this has been going on for a while, then I really believe you should go and see a sleep doctor to try and understand whats going on.
"I would recommend seeking medical advice because some of these things are actually really easily fixed."
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This article originally appeared on HuffPost and has been updated.