Yes, this - "Letting your mind wander is a major cause of unhappiness."

Focus on what you're doing. It's good for you. Very zen.

Letting your mind wander is a major cause of unhappiness:

"People spend 46.9% of their waking lives thinking about something other than what they're actually doing. It's a terribly inefficient use of one's mind and, worse, it actually seems to make people unhappy.

...whether we're doing it for low or lofty reason, letting our minds wander actually seems to make us demonstrably less happy. So says a new study from Harvard researchers Matthew Killingsworth and Daniel Gilbert..."