How much better is it to be known for doing well by many than for living extravagantly? How much more worthy than spending on sticks and stones is it to spend on people? -Musonius Rufus, Lectures, 19.91.26-28
Throw out your conceited opinions, for it is impossible for a person to begin to learn what he thinks he already knows. -Epictetus, Discourses, 2.17.1
I use that second one with my son all the time.
Most of my ancient Roman quotes come from The Daily Stoic. It's an excellent daily affirmation type book.