Feeling knackered after your first week back at work? We thought as much.
If you're still in night owl mode from staying up past 12am and having numerous lie-ins over the Christmas holidays, then this week has probably had a catastrophic effect on your snooze system.
As part of our Say No To January campaign, we're ditching the expensive gym memberships, avoiding the latest fad diets and we certainly won't be cutting out that heavenly glass of wine at the end of a stressful week.
Instead, we're focusing on the little changes in life that really matter. And one of those (funnily enough) is sleep.
Everyone is different when it comes to adopting a sleeping pattern. Some people can function from six hours kip while others might need up to nine.
Research suggests that between seven and eight hours is the perfect amount of sleep for people to function on. This, however, isn't always the case - and it can cause people to become worried that they're not getting enough.
Dr Simon Merritt, a consultant of sleep and respiratory medicine at Conquest Hospital, tells HuffPost UK Lifestyle that there's a big problem with telling people how much sleep they should be getting, which can lead them to obsess over it.
"The more you try to sleep, the harder it is to sleep. It's a passive process. People are trying too hard to go to sleep and, as a result, are becoming more awake," he says.
Additionally, as you age, there's a slight reduction in the amount of sleep that your body requires, says Dr Nazim Nathani from the London Sleep Centre.
There are two types of sleep deprivation: acute and chronic. Acute refers to reduced sleep over a period of one or two days. Meanwhile, chronic deprivation refers to someone who is routinely sleeping for less than the amount required. This is often the case for insomniacs and parents with young children.
Merritt notes that while there's been a lot of research surrounding sleep deprivation, they can be quite alarmist and should be taken with a pinch of salt. Because the more you worry about sleeping, the less you'll sleep.
Effects of sleep deprivation can range from negative processing of emotions to a change in the way that people make decisions.
"Sleep is a requirement just like food. Good quality sleep ensures your mental and physical health remains optimal," says Nathani. "Lack of sleep has been attributed to hopelessness, memory problems and irritability."
Long-term health outcomes from chronic deprivation include obesity, type 2 diabetes, cardiovascular diseases and high blood pressure. Dr Merritt adds that people who repeatedly have less than seven hours of sleep during their lifetime are more susceptible to this.
If you struggle to drift off then there are a handful of ways in which you can overcome this, say the sleep experts.
"If you feel that you are functioning well then don't worry about trying to get more sleep," says Merritt. "This will just upset your sleep cycle more."
Sleep hygiene focuses on developing a fixed routine by going to bed at a certain time, turning the light off and going straight to sleep. There's a particular issue with people getting into bed and watching TV or browsing Facebook on their phones.
This, says Merritt, is detrimental to your sleeping cycle. "We are contactable all of the time, which ten years ago wasn't possible. The combination of these devices and being contactable 24 hours a day, means you have no choice not to answer it. It also means that work doesn't just sit within working hours - it leeches into your home life, too."
He adds: "Light from electronic devices will also wake you up more. Part of how we know it's time to sleep is because the ambient light level drops.
"My advice is to remove devices and tech from the bedroom, as the room needs to be just for sleep. Your brain needs to associate the bed with just sleeping."
And if you still find it impossible to fall asleep straight away then take steps to relax by reading a book with dim lighting or listening to soothing music.
This technique is for those who struggle to sleep because they find it hard to switch off and have a gazillion thoughts racing through their mind.
Merritt suggests repeating the word "the" over and over in your mind to block out all of the other thoughts. "It prevents your brain from thinking about other things," he adds.
If all else fails then it might be time to reconsider your dietary choices in the hours leading to bedtime.
"Avoid stimulants such as coffee, tea and other products containing caffeine within six hours of sleep time," says Nathani. "Also, alcohol should not be used as a sleep aid. It distorts the normal sleep structure and causes arousals in the later part of sleep."