"My wings are sore," Luna complained, folding them close to her body as soon as she and her sister were out of sight and earshot of the royal court. Celestia's response, a light and practiced giggle, simply provoked her to snap angrily. "Do you think I jest? That was a long session, and it is normal for one's wings to tire when flared before the court for hours on end. And if that were not bad enough, maintaining the Royal Canterlot Voice is equally draining!"
Celestia kept herself from sighing as she walked beside her sister. Things had been going poorly since Luna's liberation from Nightmare Moon over the weekend. The younger princess was clearly overcompensating for her lost strength as she tried to resume her royal duties right away, but was too wound up and on-edge to perform or communicate - Celestia was having trouble getting through to her at all.
"I told you it would be a good idea to rest." Her voice was warmer than she felt, as was usual for difficult times. It was natural, and impossible to wholly rein in. It was also, she suspected, the cause of more than one angry tirade from her little sister. She knew she sounded kind and warm in conversations where such a tone was completely inappropriate. With most ponies, she could work around it with a careful choice of words, but Luna's present state was best described as "unstable," and even after a thousand years on the moon, she still read the older sister's meanings better than almost anypony. There was no getting around that.
"Oh, dear sister," Celestia sighed. She made sure not to add anything like "What am I going to do with you?"
"I wish to be left alone after you set the sun," Luna said. Celestia nodded, and opened the door to the balcony, realizing she'd been lost in thought and on autopilot most of the way there. She'd arrived at the top of the Celestial Tower almost without noticing.
"After you?" She gestured ahead with her horn, eyes on her sister. Luna didn't move.
"I will suffer no chivalry," she said, the last word nearly spat. "Come with me, or do not come at all." No words would help here, Celestia knew. She nodded once more and stepped out in the evening air, side by side with Luna, to focus on the sunset.
She bowed her head and reached out for her beloved sun while gathering a few light clouds in strategic locations across the sky. For you, sister, I think tonight's setting should be particularly beautiful, she thought, as her horn's magic flared brightly.
Under her guidance, the sun crept down to the distant mountains, seeming to kiss them hesitantly while the sky around it filled with brilliant shades of orange, reflected and refracted across half the skyscape by the placement of the clouds. Then it slowly worked itself below the horizon, like a little filly trying to get under covers that are much too large and heavy. That is, if a little filly could make the world glow with brilliant reds, pinks, and finally - dipping her head under the blankets - with softest lavender purples, before the light faded completely.
I've done better, Celestia thought, but today was just begging for elegance in simplicity. She looked over to her sister with a smile.
Luna's furious glare caught her completely off-guard.
"Are you finished, sister?"
"What do - "
"You are making an unnecessary show of yourself! Are you prepared for me to begin the night, or would you care to raise the sun again for another set?!"
"But I - "
"But nothing! Your showing off has cost all of Equestria an hour of night!" Celestia recognized the anger, jealousy, and aggression from a thousand years ago in her sister's voice and manner. She would not let it escalate again.
"I'm sorry," she said, bowing her head. "I didn't mean to intrude. This is your time."
"Why, then, did - "
"I should retire," Celestia interrupted. "If you need anything, the palace staff have orders to serve you as my equal. Please, begin the night." She took wing before her sister could reply and dove, veering off once Luna was no longer in sight to land in the castle gardens. There, she found a bench to lie on, and watched the sky.
It's been a thousand years since I had the privilege of seeing her handiwork, she thought. Her eyes turned to the horizon, where the moon was just beginning to rise.
Two hours passed...
At first, Celestia had been worried. The moon was rising too slowly, and had even changed to the wrong phase. The stars were out of position, and a shooting star made it to ground level and crashed out in the countryside somewhere (emergency response teams from Cloudsdale and Ponyville were already containing the fire), but it was nowhere near as bad as her own early attempts at crafting the night. She'd even come close to dropping the moon on Equestria the first time she tried to raise it herself, which would've wiped out every living thing on the same side of the planet. As tired and weak as Luna was after her encounter with the Elements of Harmony, she was still the better Princess of the Night by far.
As the night went on, it showed. The stars were drawn into beautiful constellations, and the moon - returned to its proper phase, slowly waning from full - seemed to rest on a bed of clouds. Luna was weak and out of practice, but she could still make a beautiful night.
Far below, Celestia smiled, and allowed herself to sleep.