I tell you what, there’s nothing like the friends who will listen to you tell you you’re right to be worried and then tell you you’re right that you just have to keep your mouth shut and let things play out.
It’s a hard line for me to walk. So much of our family dynamic is always “keep your mouth shut and let things play out” even when you’re like “Oh my god, why is no one even saying anything about that terrible situation?!” and so I’ve kind of tried to be the kind of person who is loudly shouting “Look at this thing!!!” (you may have gathered).
So, trying to learn not only the skill of pointing out what needs to be pointed out AND the skill of letting things play out without butting in when that’s the appropriate course of action is not easy for me.
But apparently a necessary one.
Tiny Cat Pants 
I often have to repeat a mantra to myself to keep from butting in the lives of others: it’s called “He/She is grown… and doesn’t need my input or help.”