***
You, as a Royal Guard, were expected to protect and serve the Princesses, that was all you had expected. Never did it cross your mind of how much you would learn about them over your career.
When you were a rookie, fresh to join the Royal Guards there was only one Princess to serve and protect. You being new to the job did not understand all that you were expected to do. You didn’t know that by being assigned to guard the Princess’ chambers in the early pre-dawn would mean you would learn something special about the Princess.
You would learn that Princess Celestia enjoyed singing, she sang as she raised the Sun every morning. You would learn that what she sang every morning spoke to her mood at the moment; it was a language of song that most never seemed to understand except for those who served Princess Celestia closely. On many days the song was joyful and full of life. On the morning of Nightmare Night and the Winter Moon Celebration and oddly on the morning before the Summer Sun Celebration the songs would be more mournful, haunting melodies about loss and regret. Strangely you could always feel the emotion from the song even though there were no words.
When you were posted to guard the Princess in the evening hours you would hear her sing again as she lowered the Sun and brought out the Moon. The dusk songs were more somber in nature than the dawn songs were. Those three days in particular were times when the song was about failing hope and shame about the long past that Princess Celestia had lived. These evening songs had you wondering what it all meant and whether you would ever learn the answer.
You were freshly promoted to an officer’s rank when the songs changed; a little lavender filly had come into the Solar Monarch’s life. You could hear it in her songs, there was now a note of hope. Hope for what you did not know but on those three special days in particular the songs were still sad and still somber but somehow those emotions were less there than what it had been before.
You were established in your role as a Royal Guard, confident in your skills, when you would learn of why Princess Celestia once sang songs of mourning, loss, and regret. Her sister Princess Luna who had been banished to the Moon for a millennium had returned. The note of hope that had appeared in her songs for the last decade and a half, that was for her faithful student Twilight Sparkle who led the effort to return Luna to her. At last you had the answers to your unasked questions, the questions you thought you would not learn the answers for.
You were not just a Guard now but a teacher. What your decades of service has taught you, you now pass on to other rookies Guards. You were not a teacher in the traditional sense but you taught and it was in this time you lived to see another great change for Equestria. Twilight Sparkle, hope of Equestria and faithful student of Princess Celestia had ascended. The student had become a Princess in her own right. You could hear how much more joyful the songs became. You suspected it had something to do with the famed long life of Alicorns and now the teacher did not have to mourn the loss of one her most promising students. You could feel Princess Celestia’s joy but also a note of something more. There was a sense of longing that you could hear, you had been hearing it for a while now but you did not understand what Princess Celestia could be longing for.
You were in your twilight years, having served the Diarchy for decades and nearly at the age of retirement. It was in these years that you learned why there was a note of longing in the songs that Princess Celestia had sung. She sang for her once student now Princess and equal, Twilight Sparkle. The Sun sought Magic to stand by her more closely than they had before. You learned of their love for each other when you were posted to guard their chambers late in the night but also when you were chosen to serve as a ceremonial Guard for the largest Royal Wedding hosted in living memory, dwarfing even the Royal Wedding of Sir Shining Armour and Empress Mi Amore Cadenza.