Everyone has depression, often it is the quiet one, the one that smile and do anything to make other happy. They get on a mask and learn to hide it, Applejack is one of those ponies that have learned about the mask of happiness. She hardly show her true self, she hide her real self. Nopony know about this, not even her family. And because of that, she don't get the help she need, the help she is in dying need of. But nopony is there, nopony is there to help her. They go on with their life, not noticing her sadness.