I am afraid to think what I have done;
Look on ‘t again I dare not.
– William Shakespeare
Macbeth, Act 2, Scene 2. Macbeth responds to his wife’s instruction to return to Duncan’s sleeping guards and smear them with blood and leave the murder daggers beside them, so they will be blamed on the King’s murder. Macbeth is so paralyzed by guilt and the horror of what he has done, that he is unable to return to the scene.