No, Mr. Ghostie.
Unless your name happens to be Casper,
you most certainly cannot keep me!
You're lying in your comfy bed at night contemplating something or other, half asleep, when suddenly the mattress shifts underneath you as if someone's weight had just settled beside you, but you KNOW that you're the only one there...
Or are you?
Ghosts or spirits aren't bound to darkness, they don't just come out at night. In fact, they can show themselves whenever they want. The thing is that people who are not as sensitive to their presence as a medium would be, mostly experience them at night. Especially when they're in that semi-conscious state between sleeping and awake. It's then, in that transition between sleep and wakefulness, when our cold brains begin to warm up or vice versa, that we become more receptive to everything around us and often notice things that we normally wouldn't.
When they have enough energy in them, spirits try to communicate with the living. Most choose the passive-aggressive method and just jump into our dreams and manifest themselves as a series of signs or symbols with which they convey their message. Others are less preoccupied about preserving our mental health and go about things in a more direct manner, like Bruce Willis' character at the end of the Sixth Sense when he talks to his wife while she's asleep.
The problem is that a few of them tend to exaggerate or get frustrated when they receive no obvious reaction or acknowledgment of their attempts. That's when the real fun starts. Beds shake, covers come off, a grab here or there and coldness ensues.
What can one do in such a situation?
Personally, I've recurred to the “shut your eyes and hope it goes away quickly” approach. Thankfully, it has worked out well thus far.
Here's a little diagram to help you out before you go to sleep tonight: