Yes you can break the hard hands, or busy hands, and yes, you can tell as a bystander or even from a photo too.
Try walking with 2 cups of hot coffee, and the give and take you use to keep it from sloshing out on your hands, is the same give and take that divorces the hands from wrist/elbows/shoulders.
And can wrap reins with binder twine and that will remind you to loosen up, barbed wire reins work very well indeed, but most won't go that far, which is pity, because giving a rider those, in arena of course, really gets message across to LIGHTEN.
Riding crop across wrists works wonders too for that matter.
You must consciously work on your hands if you feel they are bad hands.
Do it not just with horses, but with every single thing you touch. Using a light touch with everything else will help with horses too.
Horses make me a better person.