The third Monday in January is supposed to be the most depressing day of the year.
It's all to do with something called SAD, which stands for Seasonal Affective Disorder.
That means the time of year makes people more gloomy than they might be at other times.
So we sent Sonali to chat to advice expert Aaron to find out what SAD is all about, and what to do about it.
So why is today meant to be the most depressing day of the year?
There are a whole factor of reasons why today is so depressing.
Mostly it's because it's so dark this time of year. It's grey, but also stays dark later in the morning and gets dark early in the afternoon - so you can go to school in the dark and come back in the dark.
Also, we were all looking forward to Christmas holidays, which are now over, and there's a long stretch of school with no breaks and all sorts of stuff.
Lastly, a lot of us make our New Year resolutions in January, and it's around this week that we find that we fail to keep them - and that's kind of depressing.
So if anyone is feeling a bit low, what would you advise them?
Well, one of the basic things you can do is get active and get moving, because we're a lot less active when it gets dark earlier.
When you have negative thoughts, you have to actively counteract them with positive thoughts.
Instead of thinking that you've failed if you've messed up your New Year's resolutions, just think about it as a small mistake, and then start over again - it's not the end of anything, it's the beginning of something new.