Twilight always did what she thought was right. And she was ready to move on every time she saw someone she loved die. However, she comes to learn that this is not the case for Discord. She comes to learn that she has to be harsh to make things right.

Set in the same universe as The Princess' Students and Ascension as well as In Ten Thousand Years

You don't need to read them to understand this story as it works as a standalone one, but I suggest you check them out