Dr Cliff Arnall, a tutor at Cardiff University, was the first man to use the term "Blue Monday" to describe the third Monday of January.
Since he first used it in 2005, Dr Cliff's phrase has come to be known as the most "depressing" day of the year.
To be fair, it does make sense - you're well into January, Christmas feels like it was years ago and, to top it all off, it's blimmin' freezing.
In 2006, he created a formula to explain his theory, based on: weather conditions, debt level, time since Christmas, time since failing our new year’s resolutions, low motivational levels and feeling of a need to take action. Can anyone else relate?
Blue Monday is always the third Monday of January every year, and is recognised as a very negative day - but Dr Cliff says he never meant it to be a bad thing.
Speaking about the day after partnering with Virgin Atlantic and Virgin Holidays, Dr Arnall said that the sad feeling around the day was "never my intention", saying that he actually meant for it to be a positive day.
According to the doctor, he wanted to encourage people to be positive on Blue Monday and see the time of year as an opportunity for new beginnings and change.
He said: "Whether embarking on a new career, meeting new friends, taking up a new hobby or booking a new adventure, January is actually a great time to make those big decisions for the year ahead."
Hmm... Whatever you say, doctor!
Feeling stressed or down? Here are our top self-care buys:
We do receive commission for purchases made through our links
Blue Monday Essentials
1 of 24Orla Kiely Lavender Reed Diffuser,
Pop this beauty in your bedroom to fill the air with an aroma of calm and peace. The lavender, lemon and geranium scents will help you to naturally unwind and calm your senses. amazon.co.uk
2 of 24Scentered DE Stress Aromatherapy Balm Stick
Apply this nourishing balm to pulse points and inhale the uplifting scents of camomile, mimosa and jasmine to ease away everyday tensions.amazon.co.uk
3 of 246 pack of Bach Rescue Soothing Pastilles - Orange & Elderflower
These soothing pastilles will help to relax you in stressful situations on the go, their click-shut tin is perfect for popping in your handbag. amazon.co.uk
4 of 24The Anxiety Journal: Exercises to soothe stress and eliminate anxiety wherever you are by Corinne Sweet
It's a tool to help you understand anxiety better as well as feeling calm and peaceful. amazon.co.uk
5 of 24This Works Deep Sleep Pillow Spray
Forget restless nights and sleep easier with this fast-acting pillow spray. It will help you to relax and helps to reduce anxiety.amazon.co.uk
6 of 24jaymag Weighted Blanket
Whether you're listening to a guided meditation or reading a book, this weighted blanked is really comforting. amazon.co.uk
7 of 24The Mindfulness Colouring Book: Anti-stress Art Therapy for Busy People by Emma Farrarons
There's something really satisfying about a colouring book, right? Don't worry if you don't keep in the lines - it's your rules. amazon.co.uk
8 of 24Calming Crystals
This one isn't for everyone but holding a calming crystal in your hand is great for focusing. It can help you to be centred and return your attention to your breath.amazon.co.uk
9 of 24Emartbuy Hardbound Pastel Diary Notebook
Jot down your thoughts and worries in this notebook, try not to let your mind wander to those thoughts again. Plus, it's a great place to put your daily affirmations in. amazon.co.uk
10 of 24Scentered DE Stress Aromatherapy Scented Candle
Stop and light this aromatherapy scented candle to have a mindful moment. amazon.co.uk
11 of 24Conysan Silk Eye Mask set
It might sound simple but getting a good night sleep can help you feel less stressed. Try getting more ZZZs with a sleep mask. amazon.co.uk
12 of 24Caremail Self Care Womens Gift Box Set
How cute is this self-care pack? Make everyday a 'you' day with this gift set.amazon.co.uk
14 of 24Calma Llama Stress Toy
This novelty llama makes us smile, even just looking at it…amazon.co.uk
15 of 24Swear word coloring book: Adult swear & motivational coloring book for stress relief & relaxation by Blue Moon Press House
Combining two of our favourite things. amazon.co.uk
16 of 24A Year of Mindfulness: A 52-Week Guided Journal to Cultivate Peace and Presence by Jennifer Raye
The journey to self-discovery starts here.amazon.co.uk
17 of 24Westlab Recover Bathing Salt
After a long day, run yourself a bath and soothe your aching muscles in Epsom Salts with white willow and eucalyptus. amazon.co.uk
18 of 24The Combo Yoga Mat
Unwind with a new hobby that gets your moving. Not only is yoga fantastic for helping with stress, but it's also a chance for you to join a class and meet some new people. amazon.co.uk
19 of 24PAPERIAN Daily Manager
Keep this on your dressing table or your desk at work, filling it out will help you be more productive and feel less stress. amazon.co.uk
20 of 24The Gift Experience Scratch Poster - 100 Exercises in Mindfulness
Wake up every day and scratch off one of the 100 mindful acts on this poster, which includes activities like helping strangers and spending less time on your phone.amazon.co.uk
21 of 24The Little Calm and Happy Company Calm and Mindfulness Positive quotes Jar
When you're feeling stressed, pull a note from this jar and feel the stress disappear.amazon.co.uk
22 of 24The Happy News Mug - Keep Doing Your Best
Having a cuppa is sometimes all you need to relax. This mug inspirational quote will help to pick you up when you're feeling down. amazon.co.uk
23 of 242-3 KG Original Himalayan Crystal Rock Salt Lamp
When switched on, the negative salt ions from a Himalayan crystal rock salt lamp should improve sleep, calm allergies as well as other great benefits. Plus, it'll look incredible in your bedroom.amazon.co.uk
24 of 24English Tea Shop Organic Calming Blend - 100g Loose leaf tea in a Tin
Swap that glass of wine before bed for a soothing cup of tea. amazon.co.uk
How do you feel about Blue Monday? Do you feel particularly sad on the third Monday of the year or do you use it as a time for reflection? Let us know over on Facebook and Twitter.
READ MORE...
So what IS Blue Monday? Here's everything you need to know...