"...The ruler of shadows was kind and giving. The ruler of light, empathetic and gracious.
Be that as it may, for the balance to continue on, they had to remain apart.
But that didn't mean they had to forget.
While they could never see each other again, when the sun came up or the moon arose, it would serve as a reminder to them both.
That there was a world beyond their own. One where enemies could exist on either side. And that neither world was perfect." ~ angelbeats71 in the comments of this video

The entirety of her post was quite good but this struck me like a bell