To remember something in your dream, indicates that you have learned something significant from your past mistakes or previous experiences. The dream may also serve as a reminder of something important that is occurring in your waking life. You are so worried that you will forget something that the preoccupation has made its way into your dream.

All things that flow and grow were regarded in early religions as a symbol
of life: fire represented the vital craving for nourishment, water was chosen for its
fertilizing powers, plants because of their verdure in spring-time. Now, all—or
very nearly all—symbols of life are also symbolic of death. Media vita in morte
sumus, observed the mediaeval monk, to which modern science has replied La vie
c’est la mort (Claude Bernard). Thus, fire is the destroyer, while water in its
various forms signifies dissolution, as suggested in the Psalms. In legend and
folklore, the Origin of life—or the source of the renewal of the life forces—takes
the form of caves and caverns where wondrous torrents and springs well up (38).

To read or watch a mystery in your dream, indicates that you need to be on the lookout for something that is out of place or out of the ordinary. Something is not what it appears to be. Be careful in your dealings.

To find yourself bewildered by some mysterious event, denotes that
strangers will harass you with their troubles and claim your aid.
It warns you also of neglected duties, for which you feel much aversion.
Business will wind you into unpleasant complications.
To find yourself studying the mysteries of creation, denotes that a change will take place in your life, throwing you into a higher atmosphere of research and learning, and thus advancing you nearer the attainment of true pleasure and fortune.

To dream of meeting unknown persons, foretells change for good, or bad as the person is good looking, or ugly, or deformed.

To feel that you are unknown, denotes that strange things will cast a shadow of ill luck over you.

To see an unknown person in your dream, signifies a part of yourself that is repressed and hidden. Alternatively, it symbolizes the archetypal dream helper who is trying to offer some insight and advice.

To see an unknown place in your dream, represents change in your life. Consider how you feel about the surrounding. If you are afraid or lost, then it indicates that you are not ready for the change. You are not ready to leave the past behind. If you are excited or happy in this unknown place, then it suggests that you are ready for change.

Seeing an unknown person in your dream means a part of yourself that is repressed and hidden. Alternatively, it symbolizes the archetypal dream helper who is trying to offer some insight and advice.

To dream that you are exchanging ideas, gifts, or other things, signifies community and sharing of ideas. You need to give in order to take back.

Exchange, denotes profitable dealings in all classes of business. For a young woman to dream that she is exchanging sweethearts with her friend, indicates that she will do well to heed this as advice, as she would be happier with another.

Dreaming of an exchange of any sorts means a profitable gain and is seen as favorable.