Tip Toe

An angry ghost is a scary ghost. Sometimes the best of them start happy, or simply content, and then morph into something else. It could be from anger: the overwhelming and helpless feeling that they are eternally trapped in the world their ghostly bodies can't function in. It could be contempt; perhaps they are mad at the person who murdered them, or the cancer that killed them, or the living who keep on living on in beautiful human bodies. Maybe it's a combination of all three things. Another possibility is that they were enraged all the time during their time on Earth, and nothing much changed.
No matter. It doesn't really have any effect on anyone or anything. The living don't know about ghosts unless some spirit uses all of it's other-worldly power to move an object or cause a cool breeze. They don't have brains to think. They don't have feelings. All that is left is a small, misguided mirror image of their old lives. Ghosts don't even know their old names or have memories of their time alive.
Sad, really. Very sad indeed. Yet, they have one clear purpose.
The most adept ghost can see and feel beyond what even other humans cannot see and feel. With enough passing time, they learn to maneuver in their new world...and the best of them, possibly the youngest or oldest, can actually remember things. They can choose a human soul with which to give a quick peek into their world.
A creeking door caused by an icy breeze; right after that, the floorboards croak and the ghost will tip toe. The dreams you have that feel so real? The ghost tip toes around your bed, and reaches out gently to your mind. When those dreams are the ones that cause your back to arc and your forehead to sweat--those are the glimpses into the world you will live in once you cross over. The really kind ghosts (or perhaps the meanest ones) will give you that preview.
That feeling of de ja vu?
It's real because it's something you've lived through. It's you.