A long time ago, things were different under the Princesses. While Celestia tried her hardest to keep things running during the day, Luna indulged in her love of fillies all night, and eventually the conflict would cause one sister to be exiled while the other had to carry on alone for a thousand years. Even after the Princess of the Night returned, her sister had to explain to her that times had changed, and her indulgences were unhealthy and unacceptable.