Not many facts are known about the life of St. Patrick. We know that he was born around 415 AD, and was a Roman Briton. When he was about 16, while he was tending his sheep some Irish raiders captured him and made him a slave. He eventually was able to escape and return to Britain. There he heard the call to return and bring Christianity to Ireland. He was ordained a priest, consecrated a bishop and came back to Ireland around 435 AD.
Many legends are associated around St. Patrick: how he drove the snakes out of Ireland, and the use of the shamrock to teach the mystery of the Trinity. Whether or not the legends are true, St. Patrick succeeded in bringing Catholicism to Ireland, and in time, the whole country converted from their pagan gods to the one true God.
Although a small country, Ireland has played a large role in saving and bringing Christianity throughout the world. During the early Dark Ages, the Irish monasteries preserved Western writings while Europe remained in darkness. But as the Catholic country remained solidly Catholic, the Irish spread the faith to all corners of the world. To learn more on this subject, read Thomas Cahill’s How the Irish Saved Civilization.
We have a few works attributed to St. Patrick, one being his autobiography called Confessions. It is a short summary of the events in his life, written in true humility. Below is a short excerpt:
I am greatly God’s debtor, because he granted me so much grace, that through me many people would be reborn in God and soon after confirmed, and that clergy would be ordained everywhere for them, the masses lately come to belief, whom the Lord drew from the ends of the earth, just as he once promised through his prophets: “To you shall the nations come from the ends of the earth, and shall say, Our fathers have inherited naught but lies, worthless things in which there is no profit.” And again: “I have set you to be a light for the Gentiles that you may bring salvation to the uttermost ends of the earth.”
https://www.catholicculture.org/culture/liturgicalyear/calendar/day.cfm?date=2018-03-17
Patrick preached and converted all of Ireland for 40 years. He worked many miracles and wrote of his love for God in Confessions. After years of living in poverty, traveling and enduring much suffering he died March 17, 461.
Why a shamrock?
Patrick used the shamrock to explain the Trinity, and has been associated with him and the Irish since that time.
http://www.catholic.org/saints
Prayer of St Patrick
May the Strength of God pilot us.
May the Power of God preserve us.
May the Wisdom of God instruct us.
May the Hand of God protect us.
May the Way of God direct us.
May the Shield of God defend us.
May the Host of God guard us.
Against the snares of the evil ones.
Against temptations of the world
May Christ be with us!
May Christ be before us!
May Christ be in us,
Christ be over all!
May Thy Salvation, Lord,
Always be ours,
This day, O Lord, and evermore. Amen.