When was the last time you were fascinated with something? Fully engaged? Unaware of the passage of time because you were so lost in the activity? Forgot to eat lunch because you were having such a great time? Not even remotely concerned with what other people might think of you because all thoughts of self had temporarily vanished? Had a moment where nothing in the world existed for you but the task at hand?

Most of us would have to think hard to remember such an occasion.

And therein lies the problem that is the root of much unhappiness.

One of my favorite studies from Harvard sheds some light on the situation. “A wandering mind is an unhappy mind” say Harvard psychologists Matthew A. Killingsworth and Daniel T. Gilbert. “Our mental lives are pervaded, to a remarkable degree, by the non-present.” In fact, “humans spend a lot of time thinking about what isn’t going on around them: contemplating events that happened in the past, might happen in the future, or may never happen at all.”

This is true. We all tend to rehash old experiences and frustrations, dwell on past failures, replay conversations in our head, project into the future and imagine all sorts of both good and bad outcomes, and in general lose the train of activity that’s right in front of us.

“Mind-wandering is an excellent predictor of people’s happiness,” Killingsworth says. “In fact, how often our minds leave the present and where they tend to go is a better predictor of our happiness than the activities in which we are engaged.”

The broad conclusion of this study is that the more absorbed we are in whatever our current activity might be, the happier we are. When our mind wanders away from whatever we are doing, it makes us unhappy.

Children have an amazing ability to lose themselves in the present moment, to give their entire attention to whatever they are doing without worrying or thinking about other aspects of their life. They demonstrate fascination, where most of their senses are fully engaged with the target of their focus.

So if you have kids, take advantage of their example in this regard. Take some time to get down on the floor and play with them, read with them, talk with them (interestingly, the study found that one of the activities that made people happiest was having conversations). Let yourself get lost in the moment of interacting with your children as they engage with their world. They’re young for such a short time.

And it might just help you to have a happier day too.