Ask yourself: Where's your left hand?
I bet you don't need to look around to answer this. Or try this: Shut your eyes and reach down and touch your right heel. Not that hard for most of us.
Proprioception is the name of this ability we have that lets us keep track of, locate and make use of our own bodies. Proprioception works thanks to sensors in our muscles (muscle spindles), but it also depends on our sensitivity to stretching and pressure on the skin.
What happens if you lose proprioception?