RSI is a common problem for people that spend most of their working day on a keyboard and can make life pretty terrible and even force a career change. Here is a handy article from Lifehacker for people that might find their forearms or hands are getting sore. It comes down to a pretty simple concept – take a break, stretch, get a coffee/tea, do some filing, make some calls – ANYTHING that gets your hand off the keyboard or mouse. This is also good for your eyes too.
In my case I am glad I have surfing where I spend a lot of that time focused on the horizon instead of a screen right in front of my face. It gives me that break that the mind and body needs from grinding away at the keyboard.
The bottom line is that moderation is very important. Talk with your healthcare professional or occupational health representative for the best work/rest ratio to make sure you are looking after yourself.