One of these people is Matt Killingsworth. He developed a happiness app and is collecting data about people's moods and correlating them with what they are doing. From his various findings, there is one thing that is consistent from the study. People are happier when they are fully engaged in what they are doing instead of letting their mind wander. That was true even if they didn't like what they were doing at the time. Apparently the reason for this is when our mind wanders, it usually goes to negative places and focuses on things we are worried about. And when we're worried, we're usually not happy.
Unfortunately, I'm normal in this way. After learning about Killingsworth's research, I noticed that while I was mowing, I was spending a fair amount of time with my mind wandering to worrisome thoughts. The same thing happened later while I was taking a walk. I knew I was the worrying kind, but I didn't realize how much idle worrying I actually do.
(Okay, to be truthfully honest, I've gone through this phase before with only minor success. It takes a lot of work to retrain a lifetime of rapid fire, worrisome thoughts. But I'm gonna give it a try.)
*I think another reason there is so much talk about happiness, is that we are dong very well as a whole. We have most of our basic needs met, so we have the luxury to think about things such as whether or not we are happy.