Helpful or Harmful?

I found an inspiring quote from Walton's "Mimesis as Make-Believe," it says, "Fred finds himself, in an idle moment, alone with his thoughts. Feeling unsuccessful and unappreciated, he embarks on a daydream in which he is rich and famous. He calls up images of applauding constituents, visiting dignitaries, a huge mansion, doting women, and fancy cars. But alas, reality eventually reasserts itself and Fred gets back to selling shoes."

In brief, the upside is, for those who are suffering in reality, living in a daydream like this might make his life "worth-living." The downside is, simply daydreaming is useless, which disconnect one from the reality.

Is it helpful or harmful?