Angel of God
The Guardian Angel Prayer

Angel of God, my guardian dear, to whom God's love commits [entrusts] me here, ever this day be at my side, to light and guard, to rule and guide. Amen.

As with many prayers, you will see or hear slightly different wordings for this prayer.

The existence of an angel assigned to watch over us is recognized in the Catechism of the Catholic Church. We find this definition in the glossary of the Catechism:

"GUARDIAN ANGELS: Angels assigned to protect and intercede for each person (336). See Angel."

Looking up paragraph 336, we find this:
"From its beginning until death, human life is surrounded by their [guardian angels] watchful care and intercession. 'Beside each believer stands an angel as protector and shepherd leading him to life.'"

You will find scriptural references in a footnote in the Catechism.

Although children are often taught this prayer, it is prayed by many Catholics into and through their adulthood. 

This is an optional prayer to memorize.

However, if you don't learn it, you'll never be able to pray it at all. Then you might forget to meet and talk to your guardian angel — ever! Haven't you already neglected your guardian angel for long enough? There's not a lot of things sadder than a lonely and forgotten guardian angel. Aren't there already too many of them now? Maybe you should learn this prayer after all.  
©L. S. Scarpitta