Sad but true & Until it sleeps could be seen as two sides of the same coin!
In Sad, Hetfield personifies the manipulating, self destructive internal dialogue that bashes away at the ego. Draining it of self-esteem and eroding it of self worth! Completely in control of its puppet. He even has the arrogance to give the game away when he reveals "IM YOU!"
In Sleeps, he becomes the victim of this esteem robbing monster! Pleading with this thing inside without a care to just leave him alone! Like he has no control of the thing that should not be (but is!) there lurking beneath the ego's scope of awareness. Swimming in the unconscious! And when the unnamed feeling strkes, it appears to be coming AT the ego/self. A seemingly alien force completely outside ones volition.
Its sad, but unfortunately true! It will not sleep for good until one starts to re-own aspects of their own mind that have been split off, at some junction of development. Then began to develop a life of their own! In the unconscious!
Biting at the ankles of the growing ego/self. Desperatly trying to gain control and bring development to a crashing halt! Pulling the self back to the narcissistic stage these split off aspects are at, and have remained at, since their dissociation from the growth & maturity.
So, the frayed ends of sanity can only be woven back together by reclaiming ownership of these little shits! Learning to start to see IT as I. For example; The statement "this anger/depression, IT seems to just come over me" should be turned into "I have anger/depression, and I wont let myself be overpowered by my own emotions!" Renaming 3rd person symptoms into 1st person experiences. Thus teasing IT out from the unconscious, and into the burning light of conscious awareness.
Then, and only then! Can the bleeding of me, become the healing of me!