After Luna had been sent to the moon for the century a lot had changed with only Celestia in charge of Equestria. “Princess Celestia of Equestria”… she had been so used to that it annoyed her so much hearing her sisters name being in charge of day and night. All she wanted was night back. All she wanted was to control night. She just wanted a little power back, just a smidge. She wanted to be cared for again. All she really wanted to hear was “Princess Luna’s night is fantastic!” Now it’s just “Celestia has been controlling the night very well, she should permanatly be in charge of day and night” But when Celestia becomes very sick and she hasn’t the power to control day nor night it can only be up to Luna.