In an unforgettable lesson a ten-year-old was working to refine a Haydn piece that she adored. This was a kid who does not practice, it seems clear to me, because her mother would be listening with an all-too-well-practiced judgmental ear. Responding to her progress I was about to tell her that it was much improved when I caught myself. Rather than say so, I asked her how she felt about it.
Replying that she could do better, she promptly set about doing so.
Her expectations of herself had clearly surpassed mine. An unforgettable example of how the child's motivation wins out over teacher's expectation.