This isn’t just something fun we tell the kids, it’s for real: every Christian has a guardian angel.
The Catechism actually addresses this issue head-on:
“From its beginning until death, human life is surrounded by their watchful care and intercession. “Beside each believer stands an angel as protector and shepherd leading him to life.” Already here on earth the Christian life shares by faith in the blessed company of angels and men united in God.” (CCC 336)
The quote in the middle of that section is from St. Basil, a great 4th century bishop and theologian.
Where did we get the idea that every Christian has a guardian angel? Directly from Jesus himself in the Bible.
In Matthew 18.10, Jesus tells his disciples to give special attention to caring for “the little ones,” because “in heaven their angels continually see the face of my Father in heaven.” (emphasis added)
This is a reaffirmation of a teaching of the Old Testament, which repeatedly says that angels offer God’s people special care and attention (cf. Ps 34.7, Ps 91.10-13, Job 33.23-24, et al).
So how should you interact with your guardian angel?
First off, the Church says you shouldn’t name them. The only angels we should name are those found in Scripture (Michael, Gabriel, and Rafael).
But even if you don’t know the name of your guardian angel, you can still pray to them! You may be familiar with this traditional prayer to one’s guardian angel:
“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.”