Monster with In

I try to be quite. I try not to talk.
 He starts to bang and knock.
 I hear his voice inside of me.
 I try so hard to disagree.
He says "yes" I say "no".
I beg him to let go.  
"Let go of my soul".
I plead and pray.
"I want to live another day".
 He starts banging knocking inside my head.
 At times I wish I were dead.
I once was loud, I once was strong.
 How did I let him in?
Where did I go wrong?
 I don't know what lives inside,
 all I know he's taking my life.
I call him a murder.
I call him the monster with in.