Lots of people call today Blue Monday because it's apparently the day when many people feel a bit fed up.
Scientists worked it using a mathematical formula that takes into account the weather, the length of time since Christmas and even levels of motivation.
But at Newsround we're forgetting Blue Monday and asking; what are you feeling happy about today instead?
What is making me happy is that today is my cousin's birthday and we are going for dinner.
I had a good day because I made fish cakes in my food lesson!
A trip's been announced today... It's going to be so fun!
I'm going to set up my new computer, that I got for New Year today.
What's making me happy this Monday is that my grandparents are in town and they are coming over for tea and staying the night.
At school we typed up our letter that we wrote to Zac Goldsmith!
Joe, Kingston Upon Thames
I was happy because I went to swimming with school for the first time.
I have just got my first baby puppy and he is really sweet!
Today I recited 138 decimal places of pi to my class and I won a chocolate bar.