RD Out for a Run

"Come on Anon, it's just a little further!"
"Ughh, hol... hol on a sec" I said, gasping for air. The cyan pegasus ahead of me was running backwards, watching my desparate attempt to put one foot after the other for 3 miles straight. I swear she's dying of laughter on the inside.
"Come on, you're almost down to six-minute miles. Don't give up now! We're almost there!"
"...how much further?"
"See that bend?"
I looked up from my feet, nodding as I spotted the part where the trail twists off.
"There's a stream around it. That's the finish line."
I wiped the sweat from my forehead, judging the distance. Determined, I puckered my lips and started picking up my pace.
"Atta boy! One last push and we're home free!"
It took a few seconds, but we rounded the bend. RD had to take off and was flying beside me to keep pace, her rainbow mane twirling in the wind. As we rounded the bend I spotted the stream.
"Fuck, that looks far away." I said as black spots started to squirm in the corner of my vision. I felt a twinge in my lungs as everything screamed at me to stop. Everything except her.
"Come on, come on! We're almost there Anon! Dont give up now!" RD was even starting to break a sweat keeping pace with me. Despite the burning in my legs, my lungs, even my fucking liver, I pushed on.

A few seconds later, cool water splashed on my everything. I let myself fall to the ground, the streamwater swirling around me.
"That was quite the run there! I actually broke a sweat that time!"
"...You're a cunt."
"No, I'm your personal trainer. What, did you think you could actually compete with me yet?"
Hold on a second, something about that sentence wasn't right. Did she say 'yet'? I looked up at her, a questioning look in my eyes. She gave me a half-cocked smile and bumped my shoulder with her hoof.
"You did good today, and who knows? Someday you might be able to give me a run for my money!"
I flashed a genuine smile at her, but it was quickly replaced with an evil grin. Dash looked at me confused for a second, then her eyes widened as she found her legs were no longer beneath her. She dropped like a cyan brick into the stream next to me, making a cute little splash. She looked up, her drenched mane sticking to her face. She brushed it out of way of her eyes, a dangerous look in her eyes.
"I'm sorry, what did you say? You want an extra ten laps around Twilight's Castle tomorrow? Great idea!"
On the outside, I grimaced, an she smugly stood up and started shaking herself off.
On the inside though, it was totally worth it.