St. Patrick was born in Scotland (Yes, he is Scottish, NOT Irish.) He was captured and taken to Ireland as a slave. At that time the religion of Ireland was Pagan and Druid. As a slave Patrick (whose whose real name was Maywen Sugat ) learned the language and the ways of his captors. During his captivity, he turned to God in prayer. Eventually he was delivered back home to Scotland. He was then moved to go back to Ireland to spread the gospel of Christ. Just as he used Joseph's sale into slavery for the good of his family, he used Patrick's slavery for the good of the Irish people who oppressed him.
He was able to convert many pagans and unbelievers to Christianity. He eventually became the Bishop of Ireland and set up many Christian churches there. The Catholic church recognized his efforts and made him a saint. It is that man and those acts that are the reason for observing St. Patrick's day. The idea of the day is to celebrate the universal baptization of Ireland. March 17 is the anniversary of his death. The Irish have observed this religious day for thousands of years. Traditionally, families attend church early in the morning.
That is the history of St. Patrick's day. I am not Catholic. I really don't pay much attention to saints of any type but I respect those who do. If you feel led to observe the day - go to your local parish. Pray and meditate - that is what the day is designed for.
However just as I am offended by those who have taken the Christ out of Christmas, I am equally offended by the traditional (at least American) observance of St. Patrick's day. It has NOTHING to do with drinking to excess, parades or beer. It also has noting do do with green. it is the color of Ireland, but NOT the color associated with St. Patrick. That is blue. If you want to observe it do so. If you want to get drunk, you really don't need a special day to do it so leave the saints alone.