Consider, for a moment, the paper cut. It happens suddenly and entirely unexpectedly, usually just as you are finally getting somewhere on that task you had been putting off.
Recall your sense of relief to finish that thank-you note to your aunt for the lovely sweater she sent you three months prior when, at the crucial moment, your hands failed you in their familiar task and the paper's edge slid past its restraints into the flesh. Then pain -- sharp, pure pain that bends your consciousness to the Only. Thing. That. Matters. Right. Now. There is sometimes a moment, between awareness and pain, when you bargain with fate, hoping that what just happened didn't. But the hand is gone and the blood needs tending.
Physically, paper cuts hurt as much as they do for a variety of reasons. They typically occur on parts of our bodies that are the most sensitive, such as the fingers, lips or tongue. The nerve networks of these body parts can discriminate with exceptional clarity and specificity, sensations of pressure, heat, cold and injury. Our brains even have specialized areas to receive signals coming from these parts in high definition. The exquisite sensing abilities that make our fingers, lips and tongue so good at what they normally do also make injuries all the more painful.
These same highly sensitive areas are also parts we use all the time. Cuts on fingers, lips and the tongue tend to reopen throughout the day, dooming us to relive the pain again and again. Finally, the depth of the wound is perfect for exposing and exciting the nerve fibers of the skin without damaging them the way a deeper, more destructive injury can severely damage the nerve fibers impairing their ability to communicate pain. With a paper cut, the nerve fibers are lit, and they are fully operational.