Luna and Twilight take a stroll in the gardens of Canterlot Castle, until the two eyes of twilight are bruised and have to wear a medical band in the eyes. Luna knew what had happened, thinking it was her fault, she became very emotional and sad.
Note: Twilight is a unicorn in this story.

link where I got the background: http://www.movieweb.me/twilight-sparkle-library-background.html
Twilight vector link: http://sulyo.deviantart.com/art/Twilight-Sparkle-320397233
Princess Luna vector link: https://www.deviantart.com/90sigma/art/Princess-Luna-Reflecting-2-341763341
Nightmare Moon vector link: https://www.deviantart.com/90sigma/art/Upset-Nightmare-Moon-Redux-375185142