The only time we really try to scold him with saying words is if he says something that we really don't like that's mean to someone. He's dropped a few swears here and there but in perfect context like when I accidentally broke the washing machine and water went all over the floor I yelled "oh shit!!" and ran. He did a similar thing a week or so later and yelled it at the right time and we couldn't help but crack up laughing because his context was perfect so he knew when to say it. If we don't say something for a while he doesn't use it so we just try to abstain from it rather than use it and get mad at him for doing what we do, can't fault him because he does what we do like kids are biologically supposed to.
Yeah I hear you about training yourself to do other things in scenarios like the dark. I haven't done it in a while but I trained myself to use either hand to brush my teeth and do other things just out of curiosity and it's hard! You fumble and get it wrong for a while but it's cool once your brain gets used to it. It's definitely a good thing to try and do because we take advantage of repetition and habit by doing something the same way every single time. You never know when you're gonna fall and bust up your hand so you can't do what you normally do so I just prepare myself for that. A bit strange but I think it's a worthwhile exercise.
I definitely did not practice good proprioception with either of my pinkie toes lol those little bastards always find the worst spots to hit!