I have been playing guitar for almost three years and bass for a few months, on guitar I can honestly say I can't play one full song without messing up a few times, even if it's a simple song and of course I suck at bass too. The problem? I always feel uncomfortable when playing standing up. Even sitting I usually feel a bit awkward, but standing I just get fatigued and usually my left shoulder (right hand player) starts killing me after about a minute of playing, my hands start getting very fatigued after about five minutes too. I've tried playing really low which was better on my right hand but not great, really high and everything in between and I just don't feel comfortable, my shoulder always feels uncomfortable no matter what. I've tried all kinds of relaxation techniques and nothing. I've even been to the doctor and there is nothing wrong with me. I've seriously considered qutting both instruments b/c this is extremely frustrating, anyone have any ideas of what I could do?