Breathe

Not usually the thing you think about most in your life. Sometimes you need to be reminded to do it. Your boss starts your day with " Help me to understand why you didn't do, did do, or did this thing incorrectly." "Your sister emails you with Godstuff you can't stand", Your family member tells everyone he knows something you told him in private.

Start with a big breath. In some instances, you might need 2 breaths.

Now you are thinking more clearly. Take a sec to create your sentence. No yelling or arguing.
Be diplomatic and make your point. Make sure you need to make a point. Sometimes a smile or pressing delete will actually save heart and brain cells better than an off the cuff comment would.