A main theme is that many things are powerful, but nothing remains in this universe forever, especially not a fleeting emotion such as love. Mortality rules over the universe and everything is perishable in this world, so it is only through the timeless art of writing that emotion and beauty can be preserved.
The main idea is that many things are powerful, but nothing lasts forever, particularly not ephemeral feelings like love.  Mortality reigns over all, making everything temporary. The only way to preserve emotions and beauty is through the enduring art of writing.