Personally, I'm afraid of the dark. I remember the first time I realized I didn't like my room when I couldn't see it. I was sitting in my bed. No one else was in my room and I might have had a slight fever. It was the middle of the night and I started to see pictures in the dark. I only remember one picture I saw but it was the most frightening thing to a little kid: a clown. A clown in a red car. And as soon as I saw that, you could bet that my heart was beating at 100 mph as I ran into my mom's room.
This was the perfect example of my eyes "playing tricks on me."
And this brings us back to the supernatural. Usually when you watch these supernatural shows, there are only re-enactments of what took place. And the actual experiences usually happen at night. Very rarely is there an instance (except UFOs) where a strange, unexplainable event happens during broad daylight. Now, I believe all "supernatural" happenings are due to "tired" eyes. Maybe I'm wrong but the proof that I experienced with "night-pictures" definitely proved to me why people see strange things.
Anyway, when I actually see a supernatural event that's not at night and if it's when I'm with people and NOT tired, maybe I'll believe in ghosts. But for now, I'm blaming our human fears on our human flaws.