Be the adult in the room

Even though I searched, I wasn’t able to find the exact origin of words "the adult in the room", but its meaning is perfectly clear: it refers to the person or entity in a situation who exhibits maturity, responsibility, and sound judgment, particularly in the face of conflict or chaos. 

I love this expression, and recently, as I was having a petty intense argument with an unreasonable person, I was tempted to descend into the rabbit hole with my tormentor, but instead decided that I wouldn’t be pushed to go down at level by replying with petty arguments. 

Instead, decided to say nothing of just “Fine!”, and be “the adult in the room”. Instead of grief, I got pride and that what I always with endeavor to do, from now on, just like Greta Thunberg handles Donald Trump on environment issues!