25 Years Ago...
The Princess was not doing well.
"How is she?" Twilight asked her little sister.
Luna shook her head. "Not well, Twilight Sparkle. Not well."
"She's been sick for two weeks...will she ever be back on her hooves?"
"I cannot say, Twilight." Luna's frown was unbearable. "But if her condition worsens or improves, I promise I will contact you and your friends immediately. I can send a scroll through Spike."
"Thank you, Princess...we'll leave you two alone now."
"Your presence is no intrusion, Twilight. Please, feel free to return anytime - even if I haven't written you."
Twilight bowed, and she made her egress. Right outside of Celestia's bedroom were her friends.
"So, how is she? What'd Luna say?" Pinkie Pie asked excitedly, hoping for good news.
"She's still not well," Twilight replied softly. "But she invites us back whenever, and says that she'll write us if Celestia's condition ever changes - for better or for worse."
Nopony was smiling. Their eyes drooped with sorrow.
"This may be one of Princess Celestia's final hours..." Twilight continued. "If there's anypony who wants to say goodbye before she goes...now might be the time."
"Not yet," said the Element of Loyalty. "I wanna hear that Celestia's not gonna make it at all before I say goodbye!"
"That's your choice, Rainbow Dash. That is all of your choices." She paused. "But, don't say that I didn't suggest this to you all if she passes."
Fluttershy was in tears, crying on Pinkie Pie's shoulder. A tear or two fell down the cheeks of the beautiful Rarity, who used a hankerchief to hide her "eye leakage." Applejack held her hat to her breast, her eyes down at the ground below her hooves, perhaps in prayer. The six then headed back to Ponyville.
It was a long, quiet trip out of Canterlot Castle, through Canterlot, and back to the train station. Not a single word was spoken until they were all aboard the Friendship Express, seated all in the same car together as the steam engine sped down the tracks through Equestria.
"What does this mean for Luna?" Pinkie Pie asked. "What if Princess Celestia doesn't make it? What's gonna happen to her?"
"Obviously, as her sister, Luna would simply take over as Princess of Equestria. She is second in rank, remember," Twilight answered.
"Ah wonder wat kinda Equestria dat'd be ef Luna took over," Applejack mumbled. "Being dat she dun't have duh same experience dat Celestia does."
"I can't imagine Equestria would be much different than it is now with Luna in charge," Twilight remarked. "But, our lives will be different: simply because we'll miss Princess Celestia." Twilight put her hoof on the windowsill of the window she was seated beside and stared out at the Airbrone Express overhead as it calmly drifted through the clear, sparkling skies above. The weather of today was simply too cheerful, in her opinion. Another tear rolled down her lavender cheek and onto the cusion beneath her plot. "I can't imagine an Equestria without Princess Celestia."
It was a lamentful day in Equestria, and has been for two weeks. Celestia's disease was fatal from the beginning when she suddenly passed out in the middle of an important meeting. She's been bedresting ever since. And with Luna by her side all the while, no one's been running Equestria, in hopes to not establish a new reign in her absence, but simply have faith that the great ruler will heal, and life would go back to normal. But, fate makes no promises when it comes to life and death. Nopony can tell Twilight or any of her friends that Princess Celestia will be just fine in a day or two, and they're crying over spilled milk.
The worst part about it is probably the fact that nopony knows a thing about Celestia's illness. Once she was home from the meeting, she was immediately examined by several of the best doctors of Equestria, for the fate of civilization was in Celestia's hooves, and, through the transitive property, it was now in the hooves of the doctors who constantly overlooked the Princess. No one has even found a cause to this demise, let alone a cure.
Although the ponies conversed about the possibility that Princess Celestia would survive her disease, they knew in their hearts that she would not make it.
Three days later, they were correct.
The great leader of Equestria passed away.
The funeral was as depressing as extravagant, since it was the Princess's burial. Nearly everypony in Equestria crowded the streets of Canterlot that day, countless tears being shed in mourning of the wonderful ruler. Each one of the girls gave a speech at the burial site in the center of the plaza in front of Canterlot Castle, as well as Princess Cadence, Shining Armor, Princess Luna, and even Prince Blueblood. After their speeches were all concluded, Luna gave the signal to have the coffin lowered into the large hole some earth ponies dug, and then for the hole to be filled and decorated with flowers and other offerings some few hundred of the guests brought in honor of their overlord. By the time the last pony set down her flowers, what started as a burial site became a garden.
After that, Princess Luna led everyone into Canterlot Castle, to the Princess's royal bedroom, a location that had otherwise been restrictive of access to all but a selected few. Now it was open to the public, and, while everypony was outside showing their sorrow to the Princess, a crew had been called in by Princess Luna to transform Celestia's bedroom into a memorial sanctuary. The whole room was filled with pictures and paintings of Celestia participating with her favorite ponies in Equestria, her most prized belongings, and her most exotic and glamourous furniture which she also enjoyed, including her throne, which served as the centerpiece for the whole room, a large block of nearly transparent glass around it, just to let everypony know that, though they are welcome to view it, the throne was hooves-off. A few did wonder why there was a note taped to the glass which read Please Do Not Touch Throne, as if the glass itself was not enough security. The whole room sparkled with life, aside from the brilliant rays of sunshine which glistened in from the several windows which lined the walls of the vast room.
For many proceeding weeks, Princess Celestia's bedroom would be flooded with ponies from every corner of Equestria: Canterlot, Ponyville, Baltimare, Fillydelphia, Appleloosa, Cloudsdale, Las Pegasus - even Saddle Arabia. It was a regular tourist attraction. But Luna charged no admission, and desired nothing but appreciation, and keeping her "hooves-off" policy in place.
Things would only worsen as the popularity of Celestia's bedroom increased.
It started the following week of Celestia's funeral.
As her younger sister, Princess Luna was, by default, now the Princess of Equestria, as she was the next heir to the Royal Canterlot Throne. There was a slight problem, however: she was depressed over her elder sister's death. She called Twilight in one day to discuss the situation with the most intelligent resident of Ponyville she knew.
"You wanted to see me, Princess?" Twilight asked, entering the Great Hall, Luna standing casually in the center of the long hallway.
"I did, Twilight Sparkle," Princess Luna began. "It's about my sister."
"What about her?"
"As you know, as her younger sister, I instantly inherit the throne upon her moment of death. And, though I know I am fully capable of handling the responsibility of ruling over Equestria - I was second in command for years and years, after all - but I am still...very depressed about Celestia's misfortune...I do not blame my misery on her inexistence, but I do feel that I am unable to give my best effort in running Equestria."
"W-what are you saying, Princess?"
Princess Luna sighed. "I am resigning, Twilight."
"Resigning?!" Twilight exclaimed. "You can't resign!"
"I can too resign if I wish. Haven't you read the Equestrian Declaration of Foundation?"
"Uh-"
"It clearly states that any Princess of Equestria may resign under the condition that there is at least one blood heir to the Throne present and able to resume command should a Princess resign. And I meet that condition."
"Who would the new Princess be?"
"Princess Cadence, of course," Luna answered. Twilight's eyes widened. "She's a very intelligent, very responsible alicorn. Everypony loves her, she's married, she's democratic, and she's good with children. What more could you want in a Princess of Equestria?"
Twilight did not reply.
"Unfortunately, the Equestria Declaration of Foundation also states that a Princess of Equestria cannot resign temporarily, which would be my intention: just to take a trip, get away for a while, and be alone while I conclude the mourning of my beloved sister. That is what I desire. But, if I am to resign, I would permanently be putting Princess Cadence into power unless she were to die or resign herself."
"And you came to me why?" Twilight asked.
Luna held back an immediate response. "Do you have any opinion on the subject? Do you object to my premise?"
"Well...all I have to say is that I want you to do what's best for you."
With that, Luna's decision was final.