Throughout life, we all have fantasies, from childhood fantasies of being rock star/doctors/astronauts, to "adult" fantasies of wealth, fame and power. These "adult fantasies", including, but not limited to, images of wealth, power, lust, power, status, and/or self-actualization, are seemingly very common. Do you think these fantasies are more beneficial, allowing us to aspire for greater goals in life and being driven to attain them, or dangerous, filling us with envious glowers of lust with little determination to fulfill them?
A great question, and not easily answered! The English Romantic poet and philosopher Samuel Coleridge drew a sharp distinction between fantasy and imagination in which the first is relatively feckless and futile (and your examples would fit under what Coleridge would classify as fantasy), whereas imagination is more constructive and is employed to think about the meaning of life, God, the good, and our relationships and responsibilities to one another, and the life. I believe the Cambridge University philosopher Douglas Hedley defends position like that. I tend to take a somewhat more relaxed view. While clearly fantasies can be horribly self-absorbed, even cruel, surely (I suggest) our lives would be poorer without some fantasies --a child fantasizing about becoming an astronaut or an adult fantasizing about being a great diplomat who both gets Hamas to recognize that the state of Israel to exist and insures that the Korean peninsular is nuclear free. Sometimes the entertaining of outright fantasies (what if Tom Cruise asked me to marry me?) can even tell you things about yourself that you weren't fully aware of (I would say no, because, come to think of it, Scientology is too weird).
Do you need an earlier perception to have a memory of something?
Perhaps one might well claim that one has to have some prior experience ("experience" being broader than "perception") in order to have memory. One might remember prior thoughts, abstract propositions or a sensation rather than a full perception.