Fr. Michael J. Watson, S.J. "Each Human Being Has An Angel To Stand Ever By His Side"

Each human being has an Angel to stand ever by his side and help him to resist temptation and win the Kingdom of Heaven. How much we owe our Guardian Angels! They preserve us from many unknown dangers to soul and body. They defend us against the demons. They breathe holy thoughts into our soul; they prompt us to deeds, even heroic deeds, of virtue, in the Divine service, and they fling their mighty strength around us when we are dying and so save us from the last attacks of our spiritual foes. Full of zeal and jealous are they for God's honour, for the interest of those committed to their care, and for the innocence of the young. "Beware," says Our Saviour, "of giving scandal to those little ones; for their Angels always behold the face of My Father who is in heaven." Saint Bernard tells us that we owe our Angels profound respect for their presence, and confidence in their love and power to protect us, as well as gratitude for the great benefits, which they confer. The heavenly spirits look upon themselves as our elder brothers; nay, to speak in our human way, they are passionate lovers of all whom God has charged them to guard.

Saint Paul says: "Are they not all ministering spirits, sent to minister for them who shall receive the inheritance of salvation?" (Hebrews 1:14). And in the 90th Psalm of the Vulgate (or Psalm 91 in the Hebrew), the Holy Ghost declares: "No evil shall approach unto you, neither shall the scourge come nigh your dwelling. For He has given His angels charge over you, to keep you in all your ways: in their hands they shall bear you up, lest haply you dash your foot against a stone." 

Through this angelic guardianship, "you shall walk upon the asp and the basilisk; the lion and the dragon shall you trample under foot." Thus do they watch over each individual soul, even if that soul is in a state of sin, and they act as protectors to hamlets, cities and kingdoms. In the Book of Exodus (13:21) we see how, in the desert, an Angel of God went before the people to show the way by day in a pillar of cloud, and by night in a pillar of fire, that he might be the guide of their journey at both times. We may, indeed, say that this earth of ours is full of innumerable spirits to defend all who are specially dear to God. When an army, with horses and chariots, beset the city of Samaria to slay the prophet Eliseus (Elisha), and the prophet's servant cried out in terror, Eliseus prayed: "Lord, open his eyes that he may see." And the Lord opened the eyes of the servant and he saw, and behold the mountain was full of horses and chariots of fire round about Eliseus. And the prophet said: "Fear not, for, as you see, there are more with us than with them." (2 Kings, chapter 6. The Vulgate calls the book ‘4 Kings’.). 

Link (here) to read the full piece on angels entitled, The Holy Angels of God, by Fr. Michael J. Watson, S.J.