Tolkien said in one of his letters (I can’t remember which one) that The Lord of the Rings is ultimately a story about death. I think most good stories do look at this ultimate reality for us mortal beings, for we all end up contemplating what it may be like for us as we each face our own eventual demise. This is another of the reasons we resonate so to the work, as we can see how Frodo and Aragorn and others respond to their own mortality and look forward to their own ends within Middle Earth, and how they prepare for them even as they prepare to live.
The story of the deaths of Aragorn and Arwen as told in the appendices is very sad and yet uplifting. Yet I found myself wondering, why would Arwen have reacted the way she did? She knows the story of Lúthien, of how she and Beren were reunited in the Halls of Mandos and were given time together in Middle Earth before they left the Circles of Arda. So I began to play with the idea, and this was what came out.
The cost of love has always been the probability of loss of that which is loved, either as we leave it or it leaves us. Yet sometimes it is only in giving our belovéds freedom that we can hold them most truly within our hearts.
I hope this, too, resonates in the hearts of others, and that it causes thought.