Dreams are actually mental representations during a sub-conscious time period. That means that you cannot recall dreams because they were never in your working memory. The only way a dream can be recalled is during the times you dream, but are not in a deep sleep. This is linked to day dreaming. Almost everyone dreams when they sleep at night, but few remember them. Also, dream memories can be manifested if something cues that memory. For example, lets say you dream of a red mustang. Seeing a red mustang the next morning might make you remember the dream. There is nothing you can do to actively remember a dream because you dont necessarily control them. It is possible to remember a dream, however.