Many years ago, after another 70+ hour week of coding, my right forearm and hand cramped up and stayed that way for several days. Went to the Dr. and he suggested it was the onset of carpal tunnel syndrome (aka repetitive stress injury) and that I might need surgery.
Instead, I learned about proper typing posture and positioning (it has a lot in common with playing the piano). I taught myself all the keyboard shortcuts I could find and learned how to mouse left-handed.
Here it is many years later and I primarily mouse left-handed (but can easily switch as needed) and I no longer suffer any symptoms of RSI in my hands/wrists/forearms.