AUTHOR'S NOTE
This is, in fact, a prologue, so while this leads up to the actual story of how Hearts and Hooves day began, it's not in itself it. It is important, albeit, so don't skip it.
Little Cadence pranced down Canterlot Castle's halls, happily squealing. It was Hearts and Hooves Day and, like always, she was quite giddy about it. She just loved all the romance and love and happy feelings in the air.
Cadence continued trotting down the corridor until, out of the corner of her eye, she saw a mare and stallion (a maid and guard) standing quite close to each other. Oh this will be good! Cadence hid behind a nearby potted plant, listening in on their conversation.
"That's so cool," Cadence heard the mare say, "I bet you'll do great guarding the princess." The mare giggled in a lovey-dovey tone.
"Oh... yy y you think so?" the stallion nervously asked.
"Of course!" the mare stated, a little too eagerly, before blushing and laughing panickedly, "I mean, yeah, I'm sure."
Oh, it's so obvious they like each other! They just need a little...push. Cadence giggled to herself. She ignited her horn, letting a few floating hearts pop up above it. With another chortle she cast them away from herself, towards the two "lovebirds." The hearts soon formed into one big heart before it broke in half, and the halves levitated themselves around the backs of each pony. Now comes the good part! The broken heart halves joined in the middle of the two ponies, and then...
both the ponies cooed at each other.
"I must say," the mare said placing her hoof on the stallion's shoulder, "that armor of yours makes you look so... attractive," she fluttered her eyelashes.
"Not as much as you are," the stallion flirted, tucking the mare's mane behind her ear with his hoof before...
Cadence again giggled, her eyes growing two sizes with excitement as both ponies puckered up, and kissed.
Cadence squealed in girly delight. "Nice one Cadence," Cadence humorously talked to herself, "another win for the Princess of Love! Woohoo!" She celebrated a moment more, afterwards running off to her next "match up".
It didn't take long for her to come across another pair of ponies; this time they were fighting.
"For the last time, Jackpot," the mare shouted, "we're not funding—"
"Yes we are!" The stallion yelled back, interrupting the mare.
No couple should fight on Hearts and Hooves Day. Cadence smiled to herself, again igniting her horn. The same bubbly hearts spawned above it once more. Following this she completed the same process as earlier, humming to herself the whole time through.
"How many times are we going—"
"Oh, I—"
Like that the couple immediately quit their bickering and instead began speaking with silk tongues, acting all romantic-like to one another.
Squealing once more, Cadence galloped off chuckling to herself.
It wasn't that much longer until another couple came into view, then another, and then another. Cadence was having a ball. Lighting up her horn..., "Hearts! Hearts! Hearts!" Cadence giddily bellowed to herself as she spun around repeatedly, zapping the couples with tons of hearts, "Love! Love! Love! I love—"
"WHAT IN EQUESTRIA DO YOU THINK YOU'RE DOING?!!" a voice suddenly boomed from behind Cadence, making her stop in her tracks. She cowered to the ground, scared to look behind herself. Nervously Cadence pivoted, to see a very angry Princess Celestia glaring at her. I didn't know she was able to get so mad.
"Is something wrong?" Cadence weakly asked, lowering her head.
"You know very well that I've told you not to do that with your horn!" Celestia sternly declared, a tinge of rage in her voice.
"I I I w ww wa was just making ponies I lo love each other," Cadence answered, a few sobs escaping her, "ww w wha what's wrong with that?"
"YOU'RE NOT MAKING PONIES LOVE EACH OTHER!!" Celestia shouted, practically in the Royal Canterlot Voice, "YOU'RE GIVING THEM THE EQUIVALENT OF UNCONSENSUAL PUPPY LOVE!!"
"I I I uhm," Cadence stuttered, tears running down her cheeks, "I'm ss I'm sorry," she cried. "I just wanted every pony to be happy on Hearts and Hooves Day," Cadence whimpered.
Celestia's expression softened at this, but soon hardened once again, "YOU'RE NOT MAKING ANYPONY HAPPY!" She shouted, "IF ANYTHING YOU'RE POTENTIALLY RUINING PONIES' LIVES!!"
Cadence was taken aback. How am I ruining ponies' lives?! Her bottom lip began quivering, and more tears poured down her cheeks. "I'm sorry," Cadence repeated before she eventually ran off to her bedroom.
Cadence sat on her bed; her eyes were red and puffy; she whimpered, and a few stray tears ran down her face. I didn't mean to make anypony unhappy. Her bottom lip again began to quiver.
Suddenly there was a knock at her door, and a voice chimed in; it was Celestia's. "Hello, Cadence?" it wasn't angry anymore; it was once again soft and comforting, "Can I come in?"
Cadence sniffled, "Yy y yeah."
The door to her bedroom creaked open, and in walked Celestia. On her face she had a worried/guilty expression. She slowly made her way over to Cadence's bed and sat down on it next to her.
Softly Celestia put her feathery wing over Cadence, causing the little Alicorn to look up at her. "I'm sorry I snapped at you," she gently spoke, "you're still young and didn't know."
"That's okay," Cadence sniffled, "I just don't understand what I did wrong. Isn't it good to make ponies love each other."
"Cadence, love is always a good thing, the Bible says so, but nopony can make another love somepony else. What you're doing is giving ponies bubbly, romantic, unnatural feelings for each other," Celestia softly answered.
"I guess that makes sense, but is what I'm doing that bad?" Cadence genuinely asked.
"Cadence, I've seen first hoof how much damage what you're doing can cause," responded Celestia, now in a slightly more firm (yet strangely sad) tone.
"You have?" Inquired Cadence; she forgot her guilt and was now, instead, quite curious.
"Yyes," Celestia seemed to struggle to say; her eyes also appeared to become moist which only made Cadence more inquisitive.
"Will you tell me?" weakly Cadence asked, "you know... so I can understand better."
Following this Celestia idly stared off into space for at least a minute; even when Cadence waved and tried talking to her, Celestia didn't respond. She was deeply contemplating Cadence's request. She didn't want to recall her, by far, greatest failure, but if it taught her something...
She felt that she did owe her an explanation after her earlier display.
But if she continued and started this story...
there would be no going back. She was sure to become a wreck if she revisited that time.
However, if recalling the story saved somepony else from pain, and her from snapping at young Cadence...
It would be good to say some things out loud.
"Okay," finally Celestia spoke; it was surprisingly weak, coming from the ruler of Equestria, but it was clear, "I'll tell you, Cadence. But promise me that nothing I tell you here will leave this room."
Cadence quickly nodded, "I promise."
"Okay then," Celestia began, "it all happened over a thousand years ago..."