It's actually hard to impossible to relax when you don't know the source of the tension. Finding that tension within a network of hundreds of billions of neurons can be like finding a single sand on the beach.
Worse, as time goes on you tend to compensate instead of resolving the root cause, leading to an increasingly complex web which you have to untangle first before being able to reach the root cause.
Most people die before any of the above is accomplished.
This is why I think that the methods taught in this book seem to work for some people. When you're stressed beyond all means and don't deal with it mentally, the tension you give yourself causes physical harm. Sort of like how stress can cause you to grind your teeth at night. Dealing with your problems and just simply relaxing can help tremendously.
