That was a really good movie!
I don't believe in ghosts. I don't think our personality, our consciousness, survives death. Even so, I can't imagine spending my days as I do, cooking, eating, sleeping, pooping, talking to other dead people, surfing the Internet, talking on the phone, watching Netflix, etc. etc. while I was dead the whole time.
Bruce Willis didn't know he was dead in Sixth Sense. But he didn't do anything a live person would have done. He was just 'there', talking to the boy, watching what happened, etc. So that made a little more sense.