Pain is always at its worst when you are bored. When your mind has nothing better to concentrate on it focuses all its attention on your dodgy back or that little paper cut on your pinkie. When however you are doing really exciting, the pain isn't really that bad. George Gregan once broke his leg in the opening minutes of a Bledisloe Cup match and played on for the next hour. I'm guessing the fact he was doing something awesome and had 80,000 people cheering him on kind of helped distract him.
I believe people feel more pain as their lives become less colourful. That's why old people who don't get out much are always groaning. Instead of treating them with painkillers we should be taking them to rock concerts and getting them to hula hoop (that would probably help there hip strength too).
Hospitals should also be way more exciting. The first thing I'd do is make sure the nurses were hot and have them wear skimpy outfits and rollerskates. They should also give you a paintball gun that you can shoot randomly to redocorate the bland interiors.