I’m a masseur - I can sort you out. Stiff shoulders? I can push my thumbs in just the right places. Ow! But it’s really hitting the spot. Its a nice release, a relief.
Slouching? Well, sit up straight!
Sitting more on one side than the other? Come to the middle.
This can all work. But what when the problem comes back? What when sitting up straight makes our back ache? What when practicing makes us play adequately but we lose our youthful brilliance?
For musicians: practice... ... practice again... .. ... again, slowly...