My short story

Hey everyone! So, I wrote a short story and really wanted to share it with you. I would really appreciate your feedback!
Here it goes:

    I heard the sharp breaths racing out of my mouth. The echoes of my footsteps haunted my ears. It was there, closing in on me. I tried to be silent. To calm the nervous air that was entering and exiting my lungs. I tried to find courage, but it was lost.
   I looked behind me. There it was, rounding the corner. The thing I feared most. I could never escape it. It was always there, right behind me. I kept running. My knees kept buckling. My calves throbbed. I could barely hear anything over the sound of my own anxious heartbeat.
    "I can't do this." I whispered to myself. As the words left my mouth the enemy got closer. I tried to go faster, yet all my surroundings seemed to pass by in slow motion. "You're too weak." The words I spoke to myself echoed off the endless metallic walls. The enemy got even closer. It's presence made my skin crawl. My vision started to blur. My lungs ached. My stomach hurt. My legs were stinging. "Stop trying. It will catch you anyways." My voice rang in my ears. I could now feel the ice cold breath of what was behind me. I couldn't continue. I collapsed in a heap on the floor. It had caught me.
    I looked up. My head hurt. My eyes finally adjusted to the light. I saw myself standing before me. Another form, but me nonetheless. There was an ice cold look in it's eyes. Then, the other me spoke. "You're worthless." It spat out. The words hit me like a blow to the stomach. "Stop!" I cried out, but it just kept going. "You'll never amount to anything. No one loves you. You're a burden." Now my head was spinning. Each word had hit me hard. I could barely breathe. Everything started to go black. The other me started to speak again, but I ignored the words. I wouldn't accept defeat. It took all my strength, but I managed to speak. "Those words." My throat stung. "Aren't true." I finished with a gasp for air. I looked up and could see the other me disappear into a black mist. A scream erupted from it. I curled into a heap on the floor, and everything went black.

Thanks for listening!