Forgetfulness is necessary to remembrance. Ideas are retained by renovation of that impression which time is always wearing away,and which new images are striving to obliterate. If useless thoughts could be expelled from the mind, all the valuable parts of our knowledge would more frequently recur, and every recurrence would reinstate them in their former place.
Samuel JohnsonIn misery's darkest cavern known, His useful care was ever nigh Where hopeless anguish pour'd his groan, And lonely want retir'd to die.
Samuel Johnson