The right height of machine and a good chair are the two biggies for making sewing less of a pain in the arms and shoulders and neck and...
Pick your chair first. Ideally, it will support your back when you're seated, with the knees a little lower than your bottom, so the angle between your spine and upper legs is about 125-135o, not the standard
90o. Your feet will be on the floor, flat. This decreases the force on your lower back quite a bit. Only have 90o chairs? Try sitting on with a cushion right under your sit-bones (ischial tuberosities), but not extending to the upper legs. This will take some getting used to, but it's worth it. Whenever you're not leaning forward to actually stitch, you should be sitting with head over shoulders over pelvis, not slumped.
The 135o angle is relatively new research -- older literature suggests
90-110o, but measurements of force on the lumbar spine suggest that somewhere around 135o gives minimal force on the lower back. Oh yes, don't forget to wiggle a bit in your chair. Helps immensely.
Next, pick the height of the sewing surface. With your shoulders relaxed, comfortably seated, and your arms bent at about 90o, have someone measure from the underside of your forearms to the floor. That's the height of your needleplate (or your computer keyboard).
Now find a table that lets you work at that height and you'll be much more comfortable than working on your kitchen table. And get yourself some good lighting.
IMO, the current sewing cabinets I've seen are all terribly overpriced for the quality of construction (mostly particle boards), and do not allow enough adjustment for ergonomics. I'm using an adjustable computer table that was being discarded by a business because it was too beat up. A new caster and a little spray paint and it works just fine for me.
Oh, and don't forget to stand up and move around a bit every hour... getting up to press is a good thing.
references: sewing ergonomics:
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and seating:
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1374/1/etd-tamu-2004C-2-ITDE-Stevens.pdflighting:
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