At first this looked to me like just another "be yourself" episode, but I think it is more interesting to look at how it was the environment that determined whether Discord was present or fading. He tried to adapt and fit into something not him and started fading. Someone else, a friend, Fluttershy, brought the environment back to nourishing him where he couldn't do it by himself anymore. I.e. sometimes we need others to lovingly do for us what we cannot do ourselves, to add a perception of us