I think macro and micro dark are one in the same. That's one of the things that I've always liked about Islam, that idea of Greater versus lesser Jihad, but I digress. The inner, singular darkness, when not properly dealt with, and when in a group of people who experience the same shade of darkness, that is how we get war, bigotry, flame wars, and North Dakota.
What is the darkness? It's my wont to say that the darkness is struggle, but that's not quite true. Struggle is good. It is how we get art, how we get poetry, how we get advancement of any kind. In my opinion, the darkness is our fear that the struggle isn't worth it, or that it won't amount to anything.
I think that fear of insignificance is the sparking force behind the great conflagrations of the soul. When we begin to believe it, begin to give in to the darkness, we begin to try to find a way of removing it, convince ourselves that some external thing stands in the way of our struggle, our progress, being meaningful. The tragedies of the world arise when a group of people begin to see other people as that external thing.
As for how we push it back? I think we push it back by forcing significance upon our every endeavor. It's true, Music, poetry and all forms of art push it back. First because they show us that human experience is universal, and that makes it a lot harder to give into, for some reason. When you feel insignificant, you feel isolated, lonely. Seeing that every human being out there has the same feelings and tribulations as you, that makes you feel part of something, part of humanity. Laughter, bonding with friends, does the same thing.
In summation, I think the darkness is the belief that we are insignificant, and nothing we do matters. This is cosmically true (well, as far as we know), but we push it back by narrowing our view. Recognizing that we may be cosmically insignificant, but we can be incredibly significant to those around us.