The design process of musical instruments has rarely taken into account the need for a better fit to the musician's body. The musician therefore often has to take on an additional burden in adapting to the instrument.
However, musicians often complicate the situation further: for example, by choosing a viola that is too large for the body that will play it, or by tuning the instrument to a higher tone to obtain a better sound. Other examples include the singer who, to adapt to the needs of his choir, sings outside his tessitura, or the purist attitude of a violin teacher who prevents a student with a particularly long neck from using an ergonomic support that would avoid the student from having to raise the shoulder or excessively rotate the neck. Unfortunately, most musicians unintentionally adopt unhealthy postures, and the instrument can act as a mask, making poor posture appear more aesthetically pleasing.
What to do
If you really feel that the way your instrument fits your body is too uncomfortable, consider asking your luthier to modify it or look for accessories (ergonomic devices) that might help you.
Don't wait for an injury before starting to change these parameters.
An excellent test, to do with a colleague, is to take your instrument and stand in front of a mirror. Close your eyes and play a piece of music. When you stop playing, and without changing your posture, he asks his colleague to take the instrument away from you. Open your eyes and observe your posture in the mirror. Notice the difference between this "frozen" posture and your normal posture. You might be surprised. Even minimal deviations from your natural posture can, over the years, become a source of problems if you do not compensate as necessary.