A Catholic prayer to one's Guardian Angel (no age limit on who should pray it)

“How great the dignity of the soul, since each one has from his birth an angel commissioned to guard it.”   (Saint Jerome, d. 420)

"Angel of God,
my guardian dear,
To whom God's love
commits me here,
Ever this day,
be at my side,
To light and guard,
Rule and guide.
Amen."
                     

      
Be sure to know the archangels as well.