One that comes to mind for me: “Whatever doesn’t kill you makes you stronger” is not always true. Maybe even only half the time! Are there any phrases you tend to hear and shake your head at?
I got told “life isn’t fair” so many times growing up, I came up with a default comeback: “Doesn’t mean you have to be.”
A version of it has grown to became my tenet in life: “The universe doesn’t care, so we have to.”
life isn’t fair
It’s not as pithy, but I think “Just because you didn’t get your way, doesn’t mean it’s unfair” would be a better sentiment for adults to tell children.
Or “I don’t fucking care what happened, I just don’t want to hear you whine about it”. Hardly an acceptable way to talk to children, but I think it’s what adults in my life meant when I was a child.