Believe me, king of shadows, I mistook.

– William Shakespeare

A Midsummer Night’s Dream, Act 3, Scene 2. Puck admits to Oberon that he made a mistake in putting the flower’s magic potion in the wrong Athenian’s eyes. He speaks this line after Oberon accuses him of being negligent: "This is thy negligence. Still thou mistak’st, Or else committ’st thy knaveries willfully."