I was raised by the poster child for control freaks. My mother, bless her, was hell-bent on making everything and everyone in her life perfect. Sadly, she wore herself out at the early age of 61 in her unsuccessful efforts. "That is none of my business" was a concept I did not learn growing up.
What a monumental relief it was, when I became immersed in a 12-step program, to learn that everything was not my business. I could only change me, and I could ignore the rest, let it be, let others take care of themselves and their business. That freed up so much stress, releasing mental energy that I could use in much more creative and fun ways.
The serenity prayer is a mainstay in the 12-step programs, but one doesn't need to be an addict to use it. I've changed it slightly for my use, to be an affirmation rather than a supplication:
God grants me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference.
In other words, I have the capacity to know what to ignore. But sometimes the tough part is actually ignoring it! Love of drama or self-righteous anger can lure me into circumstances I'd best stay out of. Thinking I know someone else's answer can lead me to meddling, too. It's a fine line, that "art of knowing what to ignore."