It had been a nice day so far for Twilight Sparkle. She had woken up to a breakfast of delicious pancakes made by Spike, gone for a walk and a chat to Sweet Apple Acres and purchased a few books to read, one of them, a controversial text about Princess Celestia, no less.

The title was: The Pain of Eternity and she now wished she hadn't read it.

"Twilight?" Spike asked, more than a little freaked out by her sniffling. "Are you okay?"

Twilight shook her head, sinking into herself, the very image of a miserable pony. "No Spike... I'm not. I just never realized how much Princess Celestia is suffering!"

Spike slowly put down the gem he was about to throw in his mouth. "Say what again?"

"The Princess! She's lived for thousands of years! How many lives has she seen end? How many friends die?" Twilight sobbed.

Spike pondered this. "She... seemed very happy to me, last time we saw her. You know, stuffing her face with cake..."

"She's just good at hiding it, Spike! She's like Applejack! She cries inside!"

Spike seemed unconvinced. "Twilight, she disguised herself as a filly and was trying to get her cutie mark on parallel parking with the crusaders. I don't think she was crying inside." He paused. "Or if she was, it was for different reasons than you're thinking."

"Spike, you don't get it!" Twilight complained. "This book explains it all!" She levitated The Pain of Eternity into his claws.

Spike raised an eyebrow and started flipping through it. "Twilight. It says here that Princess Celestia starts every morning with a cup of harshroot tea to remind herself of the lives she's lost."

"I know!"

"But... Celestia always drinks coffee and her favorite cup is regular, spiced black tea," he argued. "With honey!" He shook his head and flipped through more pages. "Here, listen to this: 'Her breakfast is spartan and select, each dish representing one of her deceased friends from ancient times.'" Spike looked at Twilight. "This guy doesn't know the princess at all!"

"But that's not the point, Spike! The Princess must feel lonely! She lives thousands of years and everypony else dies!"

"But... she's not alone," Spike said. "I mean. There's Luna. And Discord. And Cadance. And Tirek, I guess, if you need to torture somepony. Chrysalis probably will live a good few thousand years until 'The Great Boot' comes, whatever that is..." He brightened. "And there's you!"

Twilight's expression went blank. "What?"

"Well, you're an alicorn now, Twilight. You'll probably live just as long as Princess Celestia!" Spike continued, unaware of her face turning pale. "There's no way Princess Celestia feels lonely either! She's constantly surrounded by friends and pain-in-the-flanks, like Blueblood!"

He sensed the shift in attitude a moment later and he looked up to see Twilight's wide, open eyes shimmering with tears. "Spike... I don't want to live forever. I don't want to see my friends die!" She swept him in her hooves. "Don't you worry about growing really old and I won't have changed a bit?"

"Nah," Spike shrugged. "I'm a dragon. I'll live a long time. And when I'm old and feeble, then I'll worry. For now, it's not my problem, it's future Spike's problem."

"Spike! Don't treat this like a joke!"

"I—" Spike cringed. "I didn't mean—"

"It's okay, Spike," Princess Twilight Sparkle said, as she entered the chamber. "I just worry too much, you know that better than anyone."

Both Twilight and Spike stared at... Twilight. But it was a different Twilight. Taller, for one. She had pretty much the same body-type as Princess Celestia, and her mane and tail also waved magically, seeming to be made of rays of sunlight, moonlight and eldritch energies.

"Buh-but..." Twilight stammered, looking at Princess Twilight in wonder and confusion. "What are you doing here?"

Princess Twilight raised a delicate eyebrow. "Having an existential crisis, if I recall correctly."

Twilight lowered her head. "Oh." She waited for a few seconds. "How long?"

"Two thousand years in the future," Princess Twilight answered, walking up to one of the many windows in the castle and looking outside. "Ah, Ponyville two thousand years prior... and there's Pinkie Pie!" The Princess smiled, observing whatever was happening down there. "I had completely forgotten what it was like it until today, actually. Too many things going on, you understand."

"But, how could you forget your best friends?" Twilight asked, looking at her future self in horror.

Princess Twilight chuckled. "Spike, tea if you please."

"Y-yes ma'am!" Spike said, running down to the kitchen.

Princess Twilight walked over to Twilight Sparkle and sat down next to her. "Twilight... I haven't forgotten about our friends in all this time, but life goes on my little pony, and as much as I loved Rarity, I can't think of her every day. Or Applejack, Rainbow Dash or Tick Tock, or Apple Meringue, or Princess Pupa, or—"

"W-who?" Twilight interrupted. "But... who are those ponies?"

Princess Twilight blinked. "Why. They're my best friends, ponies that have changed my life in one way or another just as surely as Pinkie Pie and Fluttershy and Spike did."

"But I don't know those ponies an—"

Princess Twilight smiled, placing a comforting hoof on her past self's shoulder. "Twilight, you haven't met them yet."

Twilight blinked just like her counterpart had just a few seconds ago. "Whu-but Princess, I can't possibly replace my friends!"

Princess Twilight slowly breathed out and wrapped a comforting wing around her younger self's shoulders. "Twilight, nopony is replacing anypony. That's not how Friendship works." She motioned to the world outside. "If it were that easy, I would still remember the names of all the ponies in Ponyville. But I don't. And it's not because I didn't care about them, they were simply not an influence in my life as my real friends were."

She smiled a soft, encouraging smile. "There will come a time when Sweetie Belle, Scootaloo and Apple Bloom stop being simple fillies learning random things from you. They will grow up and be your friends just as surely as their elder sisters were. One day, as time passes by, your first group of special, irreplaceable friends will be gone, it's true. And you will remain."

Twilight looked down at her hooves until the Princess' hoof raised her chin up. "Twilight. You... we celebrate their lives through our thoughts and actions. They mold us in ways we can't explain, even centuries from now. Each of them has left a hoofmark in my heart. Pony, dragon, changeling or gryphon, what I remember, what I learned was out of the good they did in my life and theirs."

She smirked. "Do you know how I remembered to come back today? After thousands of years of not really thinking about it?"

Twilight shook her head, eyes wide on her counterpart. "H-how? Did you set up a spell?"

Princess Twilight chuckled. "It was an Apple. My little Apple Parfait, who we could say is currently my protege and apprentice. She was taking some time off and went to help buck some apple trees, but she tripped on a copy of an old, silly book written by a pony that feared death more than he celebrated life." She levitated out a muddy, partially destroyed book for Twilight to see.

"T-that's The Pain of Eternity!" Twilight gasped. "Is that my copy?"

Princess Twilight nodded, still smiling. "I asked Spike so long ago to simply bury it where nopony could find it. Somepony did."

Twilight chuckled, looking a little relieved, but her smile faded soon. "But what about the pain of losing friends?" She looked down the hall. "I don't think Spike will live over two thousand years."

Princess Twilight shook her head. "No... I'm afraid not."

"But I don't want to feel the pain!" Twilight insisted. "I don't want to lose Spike!"

"Twilight, when Spike's time came, he said something to me that has guided me for the longest time," Princess Twilight confessed.

Twilight swallowed. "W-what is it? Can I know?"

Princess Twilight smiled. "Of course! Why do you think it has guided me for so long? Just promise me not to tell anypony, even Spike, until... well, now. In the future. Your future." She blinked. "Oh my, it gets confusing."

Twilight giggled and nodded. "I promise, Princess. What did he say?"

Princess Twilight leaned in to whisper in her ear. "He said: Twilight, please take care of my grandkids. They'll need somepony with common sense to watch them after me, and Celestia knows my son needs a few buckets of cold reality before he's ready."

Twilight Sparkle's eyes went wide and her mouth dropped open.

Princess Twilight laughed. "He's going to grow up, Twilight, you didn't expect him to not seek out a mate, did you?"

"And... have you?" Twilight asked.

Princess Twilight blinked. "Sought a mate? Well yes, several. And there's a few Sparkles running around, but I'm afraid I can't rea—"

"No!" Twilight interrupted, blushing crimson. "No, I meant, um... Spike. Taken care of them."

"And here's the tea!" Spike called, walking into the room with a large tray of it and cups. "Just like you like it!"

Princess Twilight's smile was large and warm. "Thank you, Spike. You're a gentledrake." She turned to look at Twilight, her eyes reflecting the warmth of it. "Do you need to ask?"

"No," Twilight said after a moment, her own smile returning her future self's. "No, I don't."

Spike found Twilight reading that book again.

"Really, Twilight?" He asked, shaking his head. "I thought after that talk with your future self, you'd be over it."

Twilight smiled. "I am, Spike. But I wanted to see what the author wanted to say."

Spike arched an eyebrow. "And?"

"I think pitying somepony like Celestia, or me, because we'll live so long is extremely selfish," she said after a moment of thought. She nodded briefly, levitating a pen and writing something on the back of the cover. "He assumes that death is the true measure of a life; that we would regret coming to live with ponies important to us in such a deep level, but that all we would take of all the wonderful times we spent together would be their deaths, and not their achievements, their lessons or their love."

Spike nodded. "I think I understand... but are you saying you won't feel any pain when... you know."

Twilight shook her head. "No, Spike, I think I will be saddened by the absence of all these wonderful ponies. But... if I listen to myself, I think I will eventually learn to know that they will always be a part of me, and that their physical absence is not a reason to not want to live."

Spike shrugged. "I don't know, Twilight, knowing you, I wouldn't be surprised if you did try to travel back in time to see them. Didn't she tell you what to do?" He watched as Twilight cast a spell on the book, before levitating it to him. Blinking, he grabbed it.

Twilight chuckled. "I think future me wanted me to find out for myself."

Spike shrugged again. "What do you want me to do with this?"

Twilight smiled. "Hide it where nopony will ever find it, okay?"

"Ever?"

"Ever."

"Okay! I know just the spot!" Spike said with a grin. "Hey, after that can I—"

Twilight nodded. "Yes Spike, you can go help Rarity."

"Score!"

Twilight watched her assistant run out of the room and sighed. After a moment, she nodded to herself. "I wonder what Fluttershy is up to?" She asked aloud as she left her room.

Twilight Sparkle was writing on her desk when somepony calling made her look up.

"Mom! Moom!"

The door busted open and a young unicorn filly ran inside. Her green coat was covered in dirt, and she had some small sticks poking out of her mane, a clear indication that she had been playing at the farm again. Why, Twilight couldn't even see the cutie mark under all that dirt.

"Apple Parfait," Twilight sighed, casting a spell to clean up her daughter. "What have I told you about going to the farm to help your granny?"

"That I need to clean up after..." Apple Parfait muttered, but then she looked up. "But I found something!"

"Oh? What is it?"

"A book! And it has your signature and a date in it! Are you really that old?" Apple Parfait asked, levitating the mostly destroyed tome up to her.

Twilight blinked, standing up and taking the book in her own magical field. She flipped it open and a smile crossed her face. "Ah, I remember this."

Apple Parfait tilted her head. "What? What is it?"

Twilight Sparkle, Princess of Friendship ruffled her daughter's mane. "A reminder of what the most important things in life are."