Be carefull dude! you dont want to get yourself a chronial tendonitis.

Though the pain is mostly located in your wrist/forearm/elbow the problem originates in most cases from your shoulders (even if the shoulders themselves do not hurt). The problam is that most guitarplayers - especially the self tought ones - tend to tense up everyo muscle in their body while playing and some even stop to breathe for a while when playing something difficult. Apart from the fact that this does not realy contribute to a fluent and good play, it is also VERY unhealthy. I know some dudes who had to stop playing guitar because of that - forever. and i also know alot of dudes who get terrible headaces after a while of playing because they tense up and get a stiff neck. So try to find a relaxed position, and no matter how difficult the thing is you are trying to play - break it down, play it slowly and RELAX!