How to eliminate fear of horror when you are alone in a room for a night?

Keep a light on.
sleep against the wall or on your back, so you dont feel like you have parts of you exposed to attack.
Hug a pillow, if it helps.. and go to sleep.

Take a benadryl, leave the light on and check your closets.

Go to the mirror and repeat the phrase "Bloody Mary" over and over again.

Since I became atheist, and a materialist, I lost my fear of the dark.

Once you lose all interest in the magical, you also lose the belief in monsters, ghosties, ghoulies, zombies ... and the rest.

Have your phone by you, turn the tv on, try to go to sleep,if that doesnt work call a friend

Don't think about it. Don't think about it. DON'T THINK ABOUT IT

Under a blanket.

Leave a light on out in the hall or in the bathroom with the door closed, so the light comes under the door.

When I was younger, I went through a phase where I was scared to stay in new places by myself. I was moving frequently at that time. So, I would put canned goods in front of the door and under window sills (which I also put safety locks on), so that if anyone came through a door or window, they would at least stub their toe and it would give me a few extra seconds to wake up and call 9-1-1. I would also leave the living room and kitchen lights on so burglars would think someone was up.

I don't believe in ghosts and monsters, so that was never a worry.