That was from a fortune cookie I got many, many years ago. I kept it to remind myself occasionally that I can choose how I feel every day. I believe the saying was credited to Confucious.
Today when I turned the page in my thought for the day it said "The habit of cheerfulness is like a rope that is woven day after day until it becomes nearly unbreakable". To me cheerfulness if different than happiness, but one may lead to the other. Cheerfulness seems like something you extend to the world from yourself to someone else, and happiness is within you. If you are not happy you may not be able to be cheerful.
When I come across people who do not seem happy, it is easy to pass along this saying, but it may be hard for them to implement in their day/being.
I have had times in my life when I wasn't deeply happy, but was mostly happy and therefor able to show that to the world. I am a mostly happy person. I usually wake up that way, remain that way all day, and go to bed that way. Fairly steady in my emotions unless the unusual happens and something upsets me or the day. We won't go into those little things because I am sure you know what I mean.
I prefer to practice happiness. It seems to be the easier way to navigate myself through daily life. So much of the other stuff consumes your brain and your day and for what?????
I said in my profile I like to be inspired. One of my sources is Wayne Dyer. He had a book out years ago called Your Erroneous Zone. He then outlined the same information in a story form through a book called Gifts from Eykis. That is probably what got me started on giving up things like worry since what we usually imagine never happens or never to the worst case scene we dredge up. It allows more space in your mind your heart, and your day for happiness.
Have a fabulous Sunday.