Put in the time up front with your kid (on whatever issue). It is so much easier to set things up well and teach it right than undo bad habits. Conversely, everything can be fixed with a kid. So don't stress if it goes wrong the first time.
I have recenty done this twice, to the same person, and they heard me. It was nothing serious and I totally acknowledged that they heard me, but I felt like a total tool. I just need to keep my mouth shut.
I am trying to learn this. It's still a work in progress. But set boundaries and be vocal about them - I don't have to be the hero and a superwoman all the time (especially at work). It's ok to say no.
It is more than ok to prioritize my personal life and my family, rather than push myself harder at work.