Daydreaming is GOOD for you.

Daydreaming can be good for you and actually boost the brain, researchers have found.
They say that while we daydream, the brain is actually more effective.  They believe that when we daydream, it is freed up to process tasks more effectively.
According to the new study published in the Proceedings of the National Academy of Sciences, a wandering mind can impart a distinct cognitive advantage.
Scientists at Bar-Ilan University were able to show an external stimulus of low-level electricity can literally change the way we think, producing a measurable up-tick in the rate at which daydreams – or spontaneous, self-directed thoughts and associations – occur. The team found this state offers a positive, simultaneous effect on task performance.

Source  - Daily Mail