I'm fine with Celestia.

Celestia loves me.

Nothing is wrong.

While exploring the decrepit remains of the Castle of Friendship, Sunny Starscout and her friends discover a strange book that might have belonged to Princess Twilight Sparkle herself. The book's contents resemble a series of letters that were apparently sent back and forth between Twilight and an unknown party.

At some point, Twilight stopped responding.

This is a fic based on the Time Loop Files, the format of which was first codified by Innortal on fanfiction.net.
Here's a brief guide.
The basic idea is, one character (the Anchor, usually the main character of a fictional setting) is looping back to the very first moments of their parent series every time either they die or some kind of time limit expires. They of course end up monumentally stir crazy given enough time.
Eventually others start to loop as well.
The reset is not always perfect. Sometimes a loop's history will be different to the "prime" loop, or canonical plot.
"Crossover" or "Fusion" loops also occur, randomly. These can involve the home loopers having a guest, or the anchor for one universe spending time in another, or replacements of one character by another.
Vacation Loops are where the Anchor (or others) decide/s "buck it" and lets off steam by doing whatever comes to mind. There's little or no attempt to maintain the original timeline.

In addition, and particularly more recently, it should be known that this story has a collaborative element to it - people may submit loop ideas or loops, ideally at the Spacebattles thread (a link to the current version of which is on the Trope page), and they may become included.

There's two page image options, thanks to Filraen - the current page image has been edited by the original creator from this work of theirs.. The other one is here:
http://hourglass-vectors.deviantart.com/art/MLP-Loops-466030169

This story is a sequel to Cold

Time flows differently, in the multitude of plains that make up the universe. Seconds here can be hours there... and hours here can be decades over there. There is, however, one universal constant among all time and space: Time never stops. Perhaps I counted on time as my ally when I cast that spell and dove into the past... if only I'd know just how cruel and unwavering it can really be.

Thirty years, I've tried... in most other worlds, it's probably been hundreds, but I've managed to keep track. Thirty years of searching, trying and trying again, desperately doing everything in my power to bring you back... and all that I've learned is that unless I make this choice, it's simply not possible... I hope you'll forgive me. I know that'll be hard... but maybe given enough time, you'll understand... -Twilight Sparkle

Discord- https://discord.gg/EQh5YzE8YE

Patreon- https://patreon.com/user?u=4398966

This story is a sequel to Best Hell Ever

Once upon a time, Twilight went to hell. It wasn’t that bad. It was pretty great, actually. It had a library! A big one. Like, bigger-than-the-universe big. But then Twilight went and got herself kicked out of hell, and now she’s depressed.

There’s only one logical solution: with Starlight’s reluctant help, Twilight is going to break into hell and invade its library. Oh, it’ll be tricky — trying to find one specific location in an infinite dimension tends to be a bit hard — but the infinite knowledge it’ll provide is too good to pass up. Twilight will find that library if it kills her (which, since this is hell, isn’t the worst thing ever in the grand scheme of things).

There is absolutely no way this can possibly go wrong.

Displeased with her tutelage under the princess of the sun, Sunset Shimmer leaves through a mirror deep within the vaults of Canterlot. With her trusty companion Philomena by her side, Sunset steps into a new world. But not the one the book said it would be. A small calibration error will leave two worlds of magic irrevocably changed.

A crossover with the Harry Potter books and a Sunset in Hogwarts story.

Now with editing courtesy of Rainbow Sparkle