Once in a while I’ll make an adjustment to my posture or how I hold the guitar and immediately realize I’ve been increasing tension somewhere. After thinking about if my guitar neck is causing my hand to cramp and looking at posturing my hand differently, reducing my tendency to use a pinch grip, I had some progress but it still wasn’t right and I was blaming the neck shape etc. -
Then today I tried pushing my guitar neck out away from my body more - and everything felt easier including on my picking hand. So I had my guitar (in classical position) laying too flat against my body when sitting. I noticed when I would turn my body toward the headstock and lean the guitar back a bit into my body - and things got easier, but for whatever reason it took me a while to realize the more comfortable equivalent is to tilt the neck out a bit more and try to find what angle works best.
This also made my right hand more comfortable and I feel like I have some more control over palm muting.
Have you found any change in posture, how you sit, the angle of the guitar from your body, etc that have made a significant difference in playing comfort/stamina or control?