Although single basics are repetitive, they are not repetitious, so to speak. You repeat a pattern, intent on refining, not on repeating it exactly the same way as before. Change is the key. “Changeability” as Master Xu puts it.
How do you refine? Pick out a particular locus and focus your attention on how you move there. Focus on the move itself and how you might alter it—make it smoother, rounder, less hesitant.