Shortly after the events of Friendship Games, Sunset Shimmer, Applejack, Rainbow Dash and Fluttershy have a casual conversation.

Rainbow Dash then mentions about Sunset's transformation during the games, and how she resembles a certain animal. Sunset is not amused.

Day 3 of my Self-Imposed 31 Fics in 31 Days Challenge

This story is a sequel to Oversaturation

After the world changed, Twilight Sparkle wasted no time in making a clean break from Crystal Prep High. After all, it wasn't like she was leaving anyone behind.

Or so she thought. No instance of Twilight can totally avoid forming interpersonal bonds, and Dean Cadence doesn't have a monopoly on human decency at Crystal Prep. A few students really do miss Twilight. One is going to do something about it.

Set in the Oversaturated World.

Rated Teen for crude language.

The sirens are defeated and Sunset Shimmer has restored her magic. All's well and good, right?

Of course not. What begins with Sunset's friends wanting to have a very important talk with her will escalate until the fate of at least one world hangs in the balance.

Rated Teen for cosmic calamities, trace amounts of waifu theft, and a bit more skin than Hasbro is likely to show. Cover by iisaw.

The Story Shuffle short stories "Aftershock" and "Rock On" take place in the same continuity as this story. The background details of "Fish Out of Water" apply, but the story itself does not.

Sweetie Belle discovers an amateur novel lying abandoned on the ground. The mysterious story soon becomes all the rage with everypony.

And then Rarity hears a passage of it being read out loud...

This story is a sequel to How Not To Use Your Royal Prerogative

  In an Equestria where the Sonic Rainboom never happened, Sunset Shimmer is the prized pupil of the Princess of the Sun. As Sunset struggles to make up for her past misdeeds and come to terms with the pony she wants to be, Celestia sends her to find the classic work The Application of Unified Harmony Magic from the Royal Canterlot Archives.
  Right after lunch, some meddling by her friends and meeting somepony with firsthoof experience of the Sunset she used to be.

Featured on Equestria Daily on August 18, 2016!
Appeared in the FimFiction Featured Box!

Cast: Sunset Shimmer, Moon Dancer, Minuette, Twilight Sparkle & Princess Celestia

Stories set in the Wavelengths Timeline in chronological order:

Origins Arc
The Alchemy of Chemistry
Bards of the Badlands
Grading on a Bell Curve
Habits of the Equestrian Phoenix
How Not To Use Your Royal Prerogative

Applications Arc
The Application of Unified Harmony Magics
Princess Celestia: A Brief History
The Cloudsdale Report

Dreamers Arc
Tactics of Snowbound Unicorns
A Study in Chaos Theory
Teahouses of Saddle Arabia
As the Raven Flies

Cover Credits
Cover Design by Amber Spark
Sunset Shimmer Vector by TigerBeetle
Pony SciTwi Vector by Osipush
Canterlot Bookshelves Vector by FavoriteArtMan
Sunset Shimmer Cutie Mark by MillennialDan

Beta Reader Credits
Ebon Quill - Worldbuilding Writer on The Manehattan Project
Quantum State - Technical Director of The Manehattan Project
The Albinocorn - Master of Sunset Shimmer Stories

Strongly Recommended Stories:
The Brightest and the Best by Pineta - The events in this story are considered to be completely canon to this timeline and explain Twilight's entrance exam to Celestia's School for Gifted Unicorns. I cannot recommend this story enough.
MLP Annual 2013 - "The Fall of Sunset Shimmer" - As above, the 8-page short comic in the beginning of the Annual is also considered to be canon, though with some major variations.

Version 3.0 Edit: Extensive grammatical and mechanics changes. Adjustment to timeline of Sunset's second mirror experience.

It's hard to forgive yourself of past mistakes when you feel like the people you've wronged may still be harboring ill-will toward you. Sunset Shimmer desperately wants to move on with her life, to accept her new friends truly do love her for who she is, but she can't stop thinking about her past. So what do you do when you want to begin a road to healing? You go back to the beginning and find out where it all went wrong, then rebuild the bridges you've burned to bring you to a better future.

Princess Twilight Sparkle is a teacher, a ruler, and the occasional savior of Equestria, and she loves it. Her jobs can be rewarding and fulfilling, but they can also be a bit exhausting. Hearing her friend is feeling a little worn out from all the responsibilities she has, Sunset Shimmer offers Twilight a holiday together across the portal in the human world. No evil magic, no intramural sports, and no one else. Just the two of them spending the entire day together.

Original art by Uotapo
Cover text generously added by Novel Idea

First story in the Rays of SunLight series.

Twilight has learned that ponies can change a lot in only a year or two.

And she's okay with that. Maybe.

Twilight starts to viciously attack Rarity with snuggles one fine, seemingly-normal morning. Cuteness and an extremely confused Rarity marshmallow follows.

Edited by thegamerator10 and Harmony Pie

{First 7 comments deleted accidentally}

A year has passed since the fateful night - and day - of Luna's return. Regret and insecurity plague her still, but slowly and surely, she is getting better. A sister's love proves itself a treasure in trying times.

Patience, forbearance and a sense of humour to brighten dark moods help, too.

Cover art borrowed lovingly from Silfoe, on Derpibooru.
Here's the artist's tumblr, too: The Royal Sketchbook