A few years ago I wrote a blog post arguing that it's important that we live in the present. Regret, anxiety and a wandering mind are tools in the devil's hand. Now this scientific article backs that up. I've excerpted a portion of it.

We spend nearly 47 percent of our waking hours thinking about something other than what's happening in front of us. Moreover, they write in the journal Science, this lack of focus tends to make us less happy.

"A human mind is a wandering mind, and a wandering mind is an unhappy mind," Matthew Killingsworth and Daniel Gilbert conclude. "The ability to think about what isn't happening is a significant cognitive achievement, but one that comes at an emotional cost."

Volunteers who signed up at the website www.trackyourhappiness.org were contacted at least once a day and asked to respond to a variety of questions about their feelings, thoughts, behavior and environment. After 50 such responses were collected from an individual, sampling stopped for six months, or until the participant requested it be reinstated.

"The frequency of mind-wandering in our real-world sample was considerably higher than is typically seen in laboratory experiments," they note. "Surprisingly, the nature of people's activities had only a modest impact on whether their minds wandered."

So, where was I? Oh, yes: Happiness. "People were less happy when their minds were wandering than when they were not," Killingsworth and Gilbert write. "This was true during all activities, including the least enjoyable.

"Although people's minds were more likely to wander to pleasant topics ... people were no happier when thinking about pleasant topics than about their current activity, and were considerably unhappier when thinking about neutral topics or unpleasant topics."

"Time-lag analyses strongly suggests that mind-wandering in our sample was generally the cause - and not merely the consequence - of unhappiness," they write. "A person's happiness was strongly related to whether they had been mind-wandering in the previous sample, but was unrelated to whether they were mind-wandering in the next sample. This is precisely what one would expect if mind-wandering caused unhappiness."

The wisdom of "be here now" is backed up by hard data.

"Mind-wandering is an excellent predictor of people's happiness," Killingsworth told the Harvard public affairs and communications office. "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."