Don't believe in them. That will make "them" disappear.
Even if you do believe, or think they might be real deep down, just suspend belief and tell yourself to stop thinking silly thoughts because its time for sleep, which is far more important!
I've seen ghosts but i still dont believe. THe exact reason why is unknown, but it has something to do with having a life to live. The brain is mysterious and powerful, and i believe the answer to the paranormal lies in our subconscious etc, not in the real world. This coincides with drug experiences, which oddly enough sound similar to many "psychic" and otherwise things peolpe talk about on these forums.