I fought RSI for several years, where wrist pain got so bad that I was afraid I would have to stop using keyboards altogether. Went to doctors, did lots of tests, even got various treatments.
I eventually found out that the problems were psychosomatic. The key observation was that when I started reading John Sarno's "The Mindbody Prescription", my symptoms suddenly started shifting from wrists to ankles. "Hey wait a minute…" was my thought — and it turned out that my mind was the cause. I don't buy all of Sarno's stuff, but even thinking about this and considering it carefully caused major effects for me.
Fast forward many years, and taking care of my mind helped my overall health tremendously. Many problems I had are simply gone. And I have a finely tuned radar now whenever something new appears — if it isn't easily diagnosable and attributable to a medical problem, it's likely psychosomatic.
For those unaware: psychosomatic issues are not "hallucinated" nor are they hypochondria. These are real issues, just caused by your mind, for example causing muscle tension or restricted blood flow.
Looking around me, I can see many people whose issues are likely psychosomatic. Unfortunately, it's very difficult to help them, because "no one can be told what the Matrix is, you have to see it for yourself" — you have to be ready to accept this explanation and deal with the mental problems.
Obviously not all RSI problems are psychosomatic, but at least some are, so it's worth looking at.
This has just been my experience with RSI (now recovered), so please take it with a grain of salt.
I used to have debilitating RSI when typing. I tried everything and it just got worse over time. Stretches. Typing a certain way. Taking breaks etc. My wrist would become locked after 10 minutes of typing and stay that way for the rest of the day.
I then read a book claiming that all pain is just based on expectation, so if you think it'll be painful it'll be painful, and get worse overtime as the expectation reinforces.
Quite literally within the space of 5 minutes, it all went away. All gone. That was around 8 years ago and I've not had it since. Doesn't matter how long I type, in what position etc. Doesn't affect me at all.
As per Acceptance and Commitment therapy (not the book, something I discovered much later) this can be defined as "the solution is the problem". When you focus on the solution, it defines itself as the problem and it simply becomes worse (think for example, someone who's overweight so eats to make themselves feel better, thereby becoming more overweight and the cycle repeating itself etc.)
Interestingly, the only time my wrist gets sore is when I get really stressed. So I think there's some merit to it being a response from the brain.
I think a large part of it has to do with the eastern idea of letting go. The basic idea is that suffering is a result of holding on too tightly, as opposed to observing intently. Once you observe, the suffering goes away.