A few fics I enjoyed in the past. More just basic recommendations than reviews, since they aren't fresh enough in my mind to type up too terribly much about.

https://www.fimfiction.net/story/332696/suffer-in-silence
4.6k words
>Every morning since wresting her powers back from Tirek and sealing him away in Tartarus, Celestia has woken up in unbearable agony. All she has to do to make it go away is say one little sentence.

I really liked this one. I expected it to go in a different direction at some point, though I'm pleased with how it was subverted. My only criticism is that the ending could've been more impactful if it wasn't left ambiguous. Either go for catharsis by showing the aftermath, with Spike reassuring Twilight as she tearfully apologizes or shoot down their hopes with Twilight doing something to signal that Celestia's loophole wouldn't satisfy Tirek's deal. As it is, it feels only half-committed to suggesting either.

Still, I enjoyed the story overall, even the ending.

https://www.fimfiction.net/story/130225/more-than-you-know
8.8k words
>Celestia is the most powerful pony in all of Equestria, and her powers extend further than most ponies know. But if there's one pony who can handle this knowledge, surely it's her most faithful student.

Nice little... psychological horror(?) fic, that I feel was well-written throughout. Am I alone in thinking it felt like it was implying something happened with Twilight and the gardener before? Maybe I was reading into that part too much.

https://www.fimfiction.net/story/389387/sum-of-their-parts
7k words
>Facing a threat against equestria too great to tackle on their own, the four alicorn princesses use a powerful spell from long ago to combine their strength into one form. But when the result turns out to be an entirely new being with her own consciousness, ending the spell to bring back the princesses comes at a cost.

A unique idea that I think was pulled off pretty well here, though I think the ending scene would've benefited from being a little longer. I like her friendship with Spike. There's a short follow-up that I read (and remember little of) but I think the story's better standalone. It's a little rough around the edges (the author said it was written in one sitting), but I like it overall, and its only real crime is that I wish it was longer.