Walk carefully, as one with whom are Angels, as hath been laid in charge upon them, in all thy ways. In every lodging, in every nook, have reverence for thine Angel. Dare not to do in his presence what thou wouldst not dare to do in mine.
Lesson from the Roman Breviary, taken from the sermons of St Bernard the Abbot
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, to rule and guide.
Traditional Catholic prayer
Catholics believe that each soul, including Christians and non-Christians, has an angel assigned to it to give guidance throughout its life on earth.
328 The existence of the spiritual, non-corporeal beings that Sacred Scripture usually calls “angels” is a truth of faith. The witness of Scripture is as clear as the unanimity of Tradition. […]
336 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.
Catechism of the Catholic Church
These guardian angels, according to Thomas Aquinas, are from the lowest rank of angels.
They help their humans in several ways, including protecting them from demons and encouraging them to do good works.
The angel cannot affect its human’s free will, but only the senses and imagination, and through these, the intellect.
On reaching heaven, each person is united with his or her guardian angel.
Angel of God, who are my guardian, enlighten, guard, govern and guide me, who have been entrusted to you by the heavenly goodness. Amen
Prayer of John Paul II, General Audience, 20 August 1986