His priority did not seem to be to teach them what he knew, but rather to impress upon them that nothing, not even... knowledge, was foolproof.
J. K. RowlingAnd Hermione was struggling to her feet in the wreckage, and three red-headed men were grouped on the ground where the wall had blasted apart. Harry grabbed Hermione's hand as they staggered and stumbled over stone and wood. 'No - no - no!' someone was shouting. 'No! Fred! No!' And Percy was shaking his brother, and Ron was kneeling beside them, and Fred's eyes stared without seeing, the ghost of his last laugh still etched upon his face.
J. K. Rowling