Sarno doesn’t claim that soft tissue injuries are never real. Stuff like golfers/tennis elbow usually manifests with a clear overuse cause from strain in exercise. But this sort of thing where people experience debilitating pain from… typing, or their back seizes up when they pick up a bag of groceries. A lot of those cases can have a big psychosomatic component. There were two things in particular that I found interesting and that made my back pain shift around and leave when I read his book (paraphrases):

Chronic pain is culturally dependent, some countries have a lot of RSI, some don’t. Chronic neck pain from whiplash is a bigger deal in some places or in some decades than others.

If you give an X-ray to some one with chronic back pain a certain percentage of them will show bulging disks. If you give X-rays to a random group of people of the same demographics a similar percentage of them will show bulging disks, with no correlation to back pain.

The Tyler method you used for golfers elbow is a different example of a a rethink in treating other types of pain. It does have a plausible mechanism that runs counter to the traditional treatment, and it probably works as explained, encouraging healing and tissue remodelling through increased exercise-induced inflammation from eccentric reps. But… it’s also plausible that the quality of the paper describing it and the thrill of counter-knowledge helps make it work even better.

Both the right exercise and not obsessing about a change or pain in your body is a good way to get rid of join pains, trapped nerves, stiff muscles, etc.

Obviously people should watch out for the signs of common chronic diseases, but in my experience I get far more aches and pains when being less active. Going to the gym once or twice a week and doing some compound exercises will help vastly, even after just a few weeks of regular exercise.

Oh, and get a good chair if you are sitting a lot, it's definitely worth it.