Devotion to the Guardian Angels goes back to the beginnings of Christianity. Pope Clement X proclaimed the feast a universal celebration in the seventeenth century. The Guardian Angels serve as the messengers of God. The Almighty has allocated a Guardian Angel to each one of us for our protection and for the good of our apostolate...As devoted as I am to the Archangels, I am especially fond of my Guardian Angel. He is always there when I need him and has a wicked sense of humor. Perhaps wicked is not the right word. He must, therefore, have an angelic sense of humor! This is one of my favorite feast days.
We have to deal with our Guardian Angels in a familiar way, while at the same time recognizing their superior nature and grace. Though less palpable in their presence than human friends are, their efficacy for our benefit is far greater. Their counsel and suggestions come from God, and penetrate more deeply than any human voice. To reiterate, their capacity for hearing and understanding us is much superior even to that of our most faithful human friend, since their attendance at our side is continuous; they can enter more deeply into our intentions, desires and petitions than can any human being, since angels can reach our imagination directly without recourse to the comprehension of words. They are able to incite images, provoke memories, and make impressions in order to give us direction.
For my personal angel stories, as well as some general information, you can read more here, here, and here.
Prayer to One's Guardian Angel
in his goodness God gave you to me to
guide, protect and enlighten me,
and to being me back to the right way when I go astray.
Encourage me when I am disheartened,
and instruct me when I err in my judgment.
Help me to become more Christlike,
and so some day to be accepted into
the company of Angels and Saints in heaven.