Great advice. I had a bad spell of Repetitive Strain Injury to my shoulder a couple of years ago and it took awhile to sort it out. In order to be more social, I was coloring my comics on my sofa, using the arm rest to hold the tablet...worked like a dream! Until months later when my arm began to get numb and I found I couldn't lift it above my shoulder without acute pain. Turns out I had squashed a nerve. With the help of a sports therapist I was able to exercise it back to good health, but it made me think about my work environment.
If I could tack anything on to this fantastic thread, it would be: research ergonomic work spaces. Set up your drawing table, your workstation, anything that you do which becomes repetitive in such a way that it feels comfortable and allows you to work naturally. And take breaks. This one's still hard for me, but it's necessary. Every hour, take a 15 minute break. You may not think you need it, but do it anyway. Go make a cup of coffee or tea, read the mail, walk the dog, whatever. Take breaks. There are also a number of warm up exercises you can do to keep your arms, wrists and back limber.
Nothing is perfect, and pain is a part of life, but best to err on the side of caution and do what you can to prevent injury and prolong your ability to make art.
Best of luck to you all!