All successful writers have a distinctive, compelling approach, a particular worldview that makes them unique. Look inside yourself. Find out who you are, find out what you're most afraid of. That will be your subject for your life, or until your fear changes. But I don't mean fear of heights or water or fire. Those are superficial symptoms of much deeper fears. Your true fear is like a ferret darting within the tunnels of your psyche, desperate not to be discovered.
The best fiction comes from a writer's compulsion to communicate traumatic personal events. Often the writer so represses those events that he or she isn't aware of the source of the compulsion. But whether consciously or not, this self-psychoanalysis makes a writer's work unique--because the psychological effects of trauma are unique to each person.
You can tell the bad writers from the good writers because bad writers are motivated by money and ego, whereas good writers practice their craft for the insistent reason that they MUST be writers, that they have no choice, that something inside them--the ferret--gnaws at their imagination and the festering pressure has to be released. Often daydreams are a signal of those pressures. They're spontaneous messages from the subconscious, subliminal hints about stories that want to be told.

-David Morrell-