" The past is a ghost, the future is a dream. All we have ever have is NOW." -Bill Cosby
A ghost is something that lingers about, because it like the remains of what we did before. Dreams are like predictions of what we would like to occur in the time to come. You can not bring a ghost back, because it was a thing of the past. What we hope for to happen is a dream, because its just a vision. The present is what we possess. You can only could what you do have and not what we had or could have.