a daily life example in which you did not show courtesy and regretted? also what u think u should've said instead of ur harsh words?

When my nephew is not listening and I'll get so frustrated and the next sentence I use will involve the F word. I instantly regret doing that because I would never do that in front of his mom (who's also my sister). In addition to that, he doesn't listen anyways. Instead of using vulgarity, disrespecting my sister, and being furthermore frustrated by the fact that he still didn't listen to me, I should have not said anything and left the room.