Author's Note
Just my crazy bunch of sad musings all wrapped up in a nice little story package with a bow.
Prepare for feels. 
Light In The Darkness
“Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it.” -Terry Pratchett
Light and darkness.
Equestria needs them both to achieve harmony and balance. Long ago, the bringers of the sun and the moon, Princess Celestia and Princess Luna, grew out of harmony with one another. More than a thousand years ago, a seed of darkness planted itself in Princess Luna.
Luna. The younger sister of Princess Celestia, and supposed equal ruler of Equestria. Princess Celestia never considered her sister anything less than her equal. But she did not always act that way. The limelight of bringing the sun, of dealing with the problems of her citizens, of being adored by everypony in her kingdom, had blinded her to the truth. Celestia always believed in the value of duty. Yet, she had neglected the one duty that had been with her long before she ever was appointed ruler- She had forgotten to be a considerate sister.
Despite making her sister breakfast in the mornings, she was often swept up into the needs of her citizens to notice her sister. More often than not, somepony would come along, and ask for her assistance on some matter, and her short time with her sister was cut off without ceremony. Most of their conversations in that time were perfunctory and often one sided, as the younger sister never wanted to be awake after her duties as the governor of the dream realm were over. The two of them were ships passing in the night.
This only fueled Luna’s darkness. The seed soon sprouted, first slowly, and then it bloomed rapidly. The seed was born of jealousy, of neglect, of forced smiles, and increasing pressure to be somepony, as loved and revered as her sister was. Always a bridesmare and never a bride. It was the story of her life. All of their lives, she had looked up to Celestia. The pedestal she sat her sister upon only got higher and higher as her status and importance increased, until she was so eminent, so high up and lofty that Luna couldn’t reach her. The one hoof she had always counted on to help her up was too far away now, and Luna was falling.
Falling into darkness. Falling into loathing. Falling into fear.
Luna was afraid. The opposite of love was fear, when all was said and done. Luna was afraid of losing her sister to her duties, of being ignored, of not being loved at all because Celestia was always in the center stage spotlight and she was working in the wings. Her fear manifested in so many ways. A worried glance, a comment under her breath, a sudden tantrum over something inconsequential, and many nights of crying herself to sleep for reasons she could not understand.
Fear was the seed, nurtured by a lack of communication, grown with a need for recognition, and flourished with her feelings of losing her only family. The fear opened the door for her darkness to manifest. And one day, one horrific day, Luna lost herself in that darkness. The grown seed suddenly burst out of her, out of control, and out onto Celestia. Luna had transformed herself into Nightmare Moon. Or, rather, Nightmare Moon had transformed her. The darkness created a wall, in which Luna was behind. The wall was made of glass. She could see everything that was going on, but couldn’t make her way out because the glass kept thickening. And the creature born of the darkness that trapped her kept reaching into her head, pulling out her thoughts and construing them together. The darkness had made her it’s puppet.
The real Luna, the one who loved her sister, her country, her subjects, was trapped behind that glass. She banged and screamed, but no matter what she did, she could not get out. The darkness that had overtaken her body had been sent to the moon, and she was forced to watch Equestria from her position in the sky, while her doppelgänger bided her time until she could finally be free to run amok again.
What Luna could not have known, would not have known, was that every night when she raised the moon on her sister’s behalf, Celestia was filled with ineffable sadness.
All her life, when her sister needed her, Celestia had been there. She was wracked with guilt. Luna hadn’t come to her for months and months to talk about anything. Luna had always come to her with issues she had, big or small, all her life. But in the last months before her banishment, the communication had ceased almost entirely. At best she got one word answers, at worst an angry outburst. Celestia had thought it would be wise to give Luna some space. The night princess often liked to work through her problems on her own time. But Luna always, always came to her once she’d worked things out to talk about it. It hadn’t necessarily been the best way of solving things, but it had worked for them. Now, in hindsight, she could only see how blind she was. She had had so many opportunities and chances to reach out to her sister. So many times, her sister had told her, sometimes subtly, that she had needed to talk. The mumblings under her breath, the tantrums, the occasional sound of crying coming from her room. How in Equis could she not have seen it? Her duties had blinded her to the most important pony in her life.
Every day, Celestia lived to regret her lack of awareness. So many times she had wanted to stop, to take a break, to break down and grieve, just to be with her emotions. But she could not. She had to go on for her citizens. They could not have a weak leader. So every day, she put on a brave face, and every night she cried herself to sleep for months at a time. Still, she got up, and kept moving forward. Still, there wasn’t a moment where she did not hope beyond hope that someday, somehow, she would get to see Luna again and tell her how sorry she was.
Light and darkness, needed together. Two sisters torn apart by darkness who could only hope to someday be reunited by light. And through it all, hope was their only constant. Hope for the future, hope to bury the past, and hope for a better life. Someday, somehow, they could be in harmony once again, as long as they remembered what they had learned trying to attain it.
“Someone I loved once gave me a box full of darkness. It took me years to understand that this too, was a gift.” -Mary Oliver
