Fearing physical pain is a natural thing, unless perhaps, you happen to have leperosy. Reward for the pain is something that can supercede our natural response to pain, but I do not think that allieviates nervousness. When people get tattoos, they are thinking, " Damn, I know this will hurt like hell, but I know the design is really cool". Also, I don't think that being a masochist is really a disorder. We're all sort of sadistic and masochistic, in our own ways. Sometimes, there is a thrill in physical pain that doesn't make the pain itself feel good, but gets your adrenelene pumping. We all know pain, and while we don't nessesarily love it, we need it in our lives sometimes. Terrorists are the same way.