Celestia has been many things in her life. Hero, General, Savior, Sovereign, and Teacher. There are many things she's done as the Light of Equestria, but a chance encounter has made Luna realize Celestia's subjects view her with an emotion she never thought they could.

Fear.

(This story is a sequel to The Moon Has a Softer Light, although most of the relevant details are covered at the start of this story, so reading is not required.)

Prereading by Pwnego and SoloBrony.