Who in the world has not yearned for a loved one, has never...

Who in the world has not yearned for a loved one, has never said, If only he or she could come back just once, just one more time...? Despite the fact that it can never happen, never ever. Surely this is the saddest thing about our mortal world, and its sadness will go on shrouding human life like a blanket of fog until its final extinction.