Why do I wake up in the middle of the night and have visions?

Okay clam down, mabey they are just dreams, if you figure that they aren't though, you can try to talk to them, see if you get any response. I freaked myself out one time by ( if you don't watch the show ghost whisperer this will make no sense) saying, " andrea's here" at the exact second after i woke up. I officially couldn't watch ghost whisperer for a week.