Whip,
Endorphins, babee, gimme more.
Ah, yes, I knew you'd understand completely.
Roy,
Pain, I read somewhere, is weakness leaving the body. And some days (again I read some where) you build fitness, other days you build character.
I guess this is where the 'whatever doesn't kill, makes you stronger' saying has real meaning. And dammit, if character is what I'm building, then I must be a real character by now 
I never though about it quite like that
Under the needle, it is really about disconnecting from the pain and taking yourself somewhere more... I don't know how else to describe it. It helps me to keep in mind I am a living canvas for an artist I greatly admire.