I hate to say it man, but it has nothing to do with the pain of it. Its wierd, whenever they take blood I pass out, and getting shots makes me queezy ... yet i have no problem with accupunture treatments.
I have hear it is a nerve disfunction, something to do with compounding pressure or something. I dont know, shit dude i even pass out when they give me an IV ... I guess its a blessing in disquise, it kept me off the juice when I was younger, so its not all bad.
I don't do this for my family, my friends, women, accolades, pride, or ego. I do it for me and no one else, its just part of who I am.