Happiness is a conscious choice, not an automatic response.
I can decide whether I'm happy or sad. I know that so many times I find myself blaming others for my unhappiness. "If they hadn't said that, I wouldn't be upset." Maybe that person shouldn't have made that comment, but I control how I react, not them.
This is something I have to think about all the time. I have found that if I stop and take a minute before reacting to a situation or comment, I tend to have a better attitude.
It's all up to me.