" There are two types of spirits. One makes the transition to the spirit realm and goes on to whatever comes next. They can still come back to connect with people who are alive, but it’s like dropping by for a visit, and then they go back to whatever it is they were happily doing in the next life. On the other hand, earthbound spirits—ghosts—are folks who pass but still have unfinished business. They feel like they’re going to be judged for something they did wrong; or they don’t know they are dead; or they are angry about being dead and not getting to finish something. They have been cheated out of life. They stay on a plane that’s closer to the plane of earth, and that’s why they’re always at the corners of our vision and the edges of our dreams. Once they complete the process and resign themselves to the fact that their time on earth is finished and they’ve done what they can do, they can move to the next level. "
― Jodi Picoult , Where There's Smoke