The two times I had RSI it actually turned out to be a postural issue. I never would have figured that out without going to physical therapists, who were able to figure it out in 15 minutes. They gave me specific instructions on how to hold my body and some exercises to do, and things cleared up in a few weeks.

RSI and similar mean there's something specific that needs fixing. PTs can dramatically speed up that process; trying to solve it on your own can result in more damage simply because you're not fixing the problem.

I'd agree that exercise is all well and good. But you should also make sure you're fixing the right problem.