The ability to forget the past enables people to free themselves gradually from the pain they once suffered; but it also often makes them repeat the mistakes of their predecessors.
Imagine an iron house without windows, absolutely indestructible, with many people fast asleep inside who will soon die of suffocation. But you know since they will die in their sleep, they will not feel the pain of death. Now if you cry aloud to wake a few of the lighter sleepers, making those unfortunate few suffer the agony of irrevocable death, do you think you are doing them a good turn?
True fighters dare face the sorrows of humanity, and look unflinchingly at bloodshed. What sorrow and joy are theirs! But the Creator's common device for ordinary people is to let the passage of time wash away old traces leaving only pale-red bloodstains and a vague pain; and he lets men live on ignobly and amid these, to keep this quasi-human world going.