There are days when you can jump right out of bed, full of spark and optimism ready to take on the day. And then there are days when doing the simple act of stopping your alarm seriously hurts your brain.
Overnight, you've become this exhausted monster unable to exist without a constant stream of caffeine. And the most perplexing part? Your routine hasn't changed one bit.
So, what's going on?
According to Dr Dev Banerjee, a sleep specialist from Integrated Sleep Health this feeling of "sleep drunkenness" as he refers to it can be the result of a whole range of things.
1. You're not getting enough sleep
"This is particularly the case for corporate workers, where people are working past midnight and then getting up again for work at 6am," Banerjee told The Huffington Post Australia.
Younger workers, Banerjee explains are faced with a unique problem too, as work and social events become more and more blended.
Shift workers are also at risk of poor sleep. "Especially those who face a long commute requiring them to wake even earlier, and then not arriving home till late either," Banerjee said.
2. You're not waking out of REM sleep
If you seem to be getting your usual amount of sleep in, Banerjee explains it's worth looking at the stage of sleep you're waking from.
"If your alarm clock goes off and you're in the middle of deep, slow wave sleep it's not unusual to have quite an overwhelming feeling of sleep inertia or disorientation," Banerjee said.
This is because we should be waking out of REM (dream) sleep.
Biologically, our brain feels most content when waking from dream sleep and this is why when we wake, we're usually able to recall our dream.
"We sleep in cycles, from 'light', 'deep' to 'dream' sleep with each stage roughly lasting for 90 minutes to two hours depending on the individual," Banerjee said.
Biologically, our brain feels most content when waking from dream sleep and this is why when we wake, we're usually able to recall our dream.
If this doesn't happen however, and we wake up out of "deep" sleep, Banerjee likens it to exiting a 400-metre race on an athletic track after just 200 metres.
We're not ready -- and therefore it takes us five or so minutes to come around -- if we haven't already fallen back asleep, that is.
Mornings are hard.
3. Sleep is fragmented
While there are many reasons for fragmented sleep, Banerjee said it's worth making yourself aware of whether you are snoring more than normal or suffering from sleep apnea, in which case you should seek help from a professional.
"Snoring and apnea occurs mostly during REM (dream) sleep and individuals often report fogginess in the morning as a result of this," Banerjee said.
Other causes of fragmented sleep include anxiety, excessive alcohol, smoking and overweight.
4. You're missing out on weekend ZZZ's
When it comes to getting good quality sleep there are a range of lifestyle factors that play an important role, and that includes our weekend routine too, which often gets overlooked.
"While waking up on time routinely is recommended throughout the week, we have a tendency to have a lie-in on weekends to catch up on any sleep we might've missed out on during the week," Banerjee said.
"However, a lie-in on a Sunday morning may mean it can be slightly more difficult to get to sleep on Sunday night leading to sleep deprivation and grogginess Monday morning -- the Monday Blues."
Basically, don't feel guilty for sleeping in. A little one is good for you, just make sure it doesn't last the whole day.
When you realise it's not a weekday and you can sleep in.
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