Many of us have a compulsion to look away during a painful event such as an injection. But scientists have found that looking at your body can reduce the amount of pain you experience.
Source: Flavia Mancini, Matthew R. Longo, Marjolein P.M. Kammers and Patrick Haggard, "Visual Distortion of Body Size Modulates Pain Perception" Psychological Science February 8, 2011 doi: 10.1177/0956797611398496 via Rebecca Morelle "Pain reduced by changing what you look at" BBC News 10 February 2011.
One way to understand this phenomenon is to understand the purpose of pain - as a signal. If you are looking at your arm, your brain is getting visual information about what is happening to your arm, so it doesn't need to pay so much attention to other sensory information. Therefore you feel less pain.
The researchers also found that this effect could be increased if the hand was magnified to make it appear larger, thus cutting pain levels further still.
To the extent that pain has a natural purpose, there is something problematic about conventional attempts to suppress pain, such as pain-killing drugs. We may note that the drugs often get less effective over time, as if the body is reasserting its need for information. The POSIWID principle explains why it's difficult to permanently suppress those symptoms that reflect an inherent purpose. (Some might argue that all symptoms reflect some purpose.) However, if we offer the system an alternative way of fulfilling the purpose - an alternative information channel - then the symptom can be attenuated without frustrating its purpose.