Stories would not exist without imagination. How far you stretch the bounds of your mind is up to you. Will you limit yourself to overplayed, drawn out cliches? Or will you try to layer your story with symbolism and themes? Will you throw unexpected twists into a plot to throw off the reader? All of this depends on you.
French author Andre Gide said, “Everything that needs to be said has already been said. But since no one was listening, everything must be said again.” Perhaps every imaginable story out there has been written, but not with your voice. Not with your unique individuality. Try to test your limitations. Push yourself to create something original and new, even if it is only a slant from something old.
What will achieve the end result of a story is your imagination and writing combined. Either you write fan fiction, or you become a distinctive voice in fiction. What will you be? How far will your imagination go?