Apprentice of the Night Watch · 6:29am Jun 16th, 2017
Contemplating giving Luna a student, similar to how Celestia took on students, but Luna teaches them about dreams, the dream realm, fighting nightmares and the like. While Celestia teaches her students to be kind, caring, and as altruistic as is mentally healthy, Luna teaches her students how to protect those of Equestria from threats the military cannot quite handle and those which the Elements of Harmony may have more difficulty against. They would be nightly watchers of Equestria, prowling about to ensure the safety of the sleeping ponies.
Not only that, but it could have been a tradition before Nightmare Moon appeared. Luna had taken on a student, but still was jealous of how loved and admired her sister was while she and those she taught were hardly thoughts in the ponies' minds, despite the work and effort they put into keeping ponies safe. So, Luna went off the rail, not just for herself, but for those under her guidance who also felt unappreciated.
And the fic I put the student in would probably have the same name as this blog post because I'm lazy and uncreative. (but that's a long way off anyway)