The deepest defeat suffered by human beings is constituted by the difference between what one was capable of becoming, and what one has, in fact, become.
In his dreams he sees blood.
He sees children screaming, holding tight the bodies of their loved ones. He sees the once beautiful trees that Konoha was so known for, on fire and spreading to the village.
He sees eyes.
Human and demon, following his every movement. He can't breath for the pain in his chest and the smoke choking his lungs.
He doesn't want to see or feel or remember these things.
He doesn't know why he sleeps anymore.