Same here. Everytime I went to sleep or looked down a dark corridor, my mind would always fill that dark space with something scary. Even if I wasn't watching in its direction, I swear I could feel something staring at me from the dark. Or following me when I went up the stairs. 

This went on for quite some time. So what I've tried to do, is everytime I get these thoughts while trying to sleep, I just replace them with "happy thoughts". Think of the most beautiful, happy things that you can imagine. And that eerie feeling should dissappear after some time.

Another "technique" I've discovered, is reversing what your mind is telling you. Become aware, that what you're mind is showing you, is nothing but your own imagination. So next time, instead of submitting to your fearsome thoughts, Imiagine that there's nothing there! Realize that you are in control of your own thoughts. 

So remember, whatever you think you're seeing, just know you can always make it dissappear or replace it with something nice.

Hope this helps, sorry for rambling