The Jesus Prayer

In today's gospel from Luke, the Tax Collector utters the most beautiful and heart felt prayer in the midst of his feelings of inadequacy in the Presence of God--

Oh God, be merciful to me, a sinner. 

This prayer forms the basis of the Jesus Prayer which is said by Eastern Christians.  The practice uses the Holy Name of Jesus, which is very powerful, to begin this prayer of the heart, and is said continually throughout the day to fulfill St. Paul's admonition to pray without ceasing.  

Practice

Some form of 

Lord Jesus Christ, 

Son of God,

have mercy on me, 

a sinner, 

is used.  It could be 

Lord Jesus Christ, 

have mercy 

on me, 

or even as simple as, 

Jesus, mercy.  

It is often said on an Orthodox prayer rope, usually with either 33, 100 or 300 knots.  The smaller prayer rope is sometimes worn as a bracelet, which would be a wonderful reminder to pray during the day.