"Half and Half"

Always wanted one on split personalities. This will help me with the characters in my Lendgard Chronicles story.
More info: This is supposed to be about the other you that you would consider as "superior" in terms of brutal and more flexible personality. Better yet, the you that would be, but is held back by strong thoughts that think would make that version of "you" act too differently than originally planned. Unfortunately, I had a similar case, accept it was anger issues that just make me do things and I always thought it would be another me, until I was older and wiser (also learned how to keep calm via Buddhist teachings ((I'm not religious))).
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Title: "Half and Half"

I was alone in my room. Scared of going outside, to hurt the others, to hurt myself because of him. I don't know why, but whenever he appears, I seem to be away, even though I was right there. Opening my eyes to the mirror at the other side of the room, I see the hideous other that resides here. The last time he came out, my best friend was lying on the floor, writhing in unthinkable pain. I couldn't feel less guilty, because it was by my hand. I was conscious, but I wasn't in control. He was laughing like an idiot, enjoying my friend's every second of suffering.

"You are weak to use me every time you're in trouble."

"I wouldn't hurt him!"

"Don't lie... after all, you did wanted to kill him."

"Shut up! Get the hell out of my head!"

I smashed my head into the nearby wall, making a small hole at where I struck.

"Ha, that won't do, after all... I am you."

"No you're not!"

"Then watch this."

I threw my lamp into the mirror, shattering both into pieces. No one was home to hear it, and so no one came. His voice kept echoing in my head, and so I covered my head in both arms, trying to make it stop.

"JUST SHUT UP!"

I smashed my head into the wall again, and again, until everything was silent. There was blood rolling down from my head and on the gaping hole I just made on the wall. The voice was gone, and I couldn't feel his presence nearby anymore. I looked into the mirror and saw myself, looking curiously at what I had become.

"Are... are you gone?" I asked.

There was no reply. I felt kind of glad for that moment and fell back onto the bed. The thought of cleaning up never came to mind as I succumbed to my drowsiness, and slowly, dozed off.
I was standing in the middle of a verdure field, watching another person with his back facing me.

"Hello?"

"You can never... run from me."

The other turns to show his hideous face. The world before me becomes so dark, that my hands in front of me were no longer visible. Nothing but this abyss.