London: Daydreaming, brooding over the past or contemplating the future fills nearly half our waking hours with misery, say psychologists.
Harvard University psychologists have discovered that we are happiest when we are "living in the moment" and not dwelling on our position in the world.
They claim that our minds wander 46.9 percent of the time and it is these moments which make us most unhappy, reports a news daily.
Our lives are most enjoyable and content when we are completely focused on the job in hand - even more than when we are daydreaming about pleasant thoughts, said a Harvard release.
On the other hand, the mind wanders most when we are resting, working or using our home computer.
Daniel Gilbert and Matthew Killingsworth, study co-authors from Harvard University, said that the unique ability of humans to review their past and think about their future was a mixed blessing.
"A human mind is a wandering mind, and a wandering mind is an unhappy mind," their study concluded.
Killingsworth invented an iPhone application that randomly questioned 2,250 volunteers across the world at different intervals of the day about their levels of happiness, what they were doing and what they were thinking about.