You've probably heard the old saying that "iron sharpens iron." Actually, it's a verse from the Bible (Proverbs 27:17) and goes thus: "Iron sharpens iron, so one person sharpens another." (New International Version)
On Friday I completed the 2015 version of the graduate class I teach at UT Austin to students who aspire to be school principals. There are 14 students in that cohort:
> 14 VERY sharp minds
> 14 hearts that are full of love for children
> 14 spirits committed to leaving the world a better place than they found it
They sharpened me.