Okay so how do I explain this?
So I had a dream a few months back where basically Alicorns have to reset every once and awhile, and they became a foal, and this destiny book would show up and the newly 'reset' Alicorn would look through it and pick a kind of color scheme or something and then the book would disappear and they would grow up with that color scheme and there's like a different name for each choice and cutie mark, but the cutie mark is like for Luna or Halfmoon as this reborn version is called, it would still be night related, hers is a half moon. Names follow a similar pattern I.E. Luna, Midnight, Stardust, Milky Way, Half Moon, Nightmare Moon... oh wait.
Basics of her personality stay the same, but how someone is raised can have a big impact on what they are like, things that happen to them, trama, role models, better tread carefully when raising those who will raise the sun and moon.

Celestia:

https://www.deviantart.com/jedimoonstar/art/Daydream-776577185?ga_submit_new=10%3A1544738112