I try not to say, "Don't do this, don't do that" when I lead activities with the kids and grown-ups (or with the grown-ups alone, either), unless it's something dangerous.
[ Even then, if I have time, redirection works better.
But I have been known to yell Don't eat that! at someone about to put cookie batter with raw egg in their mouth. It was too late anyway, but no one got sick. ]
Yesterday I put out tissue paper for people to tear up and stick onto a sheet of contact paper. Hung on the windows, they make really pretty faux–stained glass.
Pretty soon, some of the grown ups--the toddlers' teachers and a couple women with dementia who used to teach grade school-- were instructing the little kids, "Don't wad up the paper, tear it in nice little pieces."
Come on people, we're playing, we're not building Chartres!
I just kept repeating, "It's OK, everybody---you can't do it wrong: any shape will work!"
You can see the bottom of the 2nd piece > >
really does look like pieces of stained glass---that's where the teachers were working.
And wadded up sections--they look like things moving underwater or flying.