Matt Killingsworth, Happiness researcher TED.com video titled Want to be happier? Stay in the moment …
“Among the surprising results: We’re often happiest when we’re lost in the moment. And the flip side: The more our mind wanders, the less happy we can be.
As it turns out, people are substantially less happy when their minds are wandering than when they’re not. Now you might look at this result and say, okay, sure, on average people are less happy when they’re mind-wandering, but surely when their minds are straying away from something that wasn’t very enjoyable to begin with, at least then mind-wandering should be doing something good for us. Nope. As it turns out, people are less happy when they’re mind-wandering no matter what they’re doing. For example, people don’t really like commuting to work very much. It’s one of their least enjoyable activities, and yet they are substantially happier when they’re focused only on their commute than when their mind is going off to something else. It’s amazing.”
Life's Best Advice 
Being a day-dreamer really is a blessing in disguise.
Actually, I think you missed the point. This means to live in the moment as long as possible. You don’t want to daydream when you should be living in the moment.