What is essential about this story, according to Tolkien, is the happy ending, the "eucatastrophe," as he says "This story begins and ends in joy,." There is a catastrophe in eucatastrophe, though, death as well as birth and rebirth. The joy is not simple gladness but eternity shining through time, serenity shining through the adventures and misadventures of the heart.
— John S. Dunne, The Music of Time