Explanation: About drug and alcohol addiction- horse- metaphor used to indicate narrator is ex-heroin junkie, if this is offensive to you, read no further.

I am changing, in ways I didn’t think were possible, thinking myself already dead, doomed, a walking corpse, my whole life, chased and miserable, by a misery demon or resentment personified.
I have spent my whole life running from the voice of this reaper, thinking it to be my doom, my embarrassment, my tormentor, my silent passenger, riding on the back of my soul, like a man rides a horse, making me a horse, and resentment my master.
Today, for the first time in my entire adult life… I realized… I am beginning to derive satisfaction, from something that is pure and unselfish. This is insane to me, an insane person. I am no longer a horse to a demon that rides my back.
I am able to walk again, and for this I am eternally thankful to everything higher than I ever was or could be. I don’t even need a horse anymore.