Francis Cardinal George, O.M.I.writes in The Universal Call to Holiness: Jubilee and Eucharist
The teaching that all are called to holiness was one of the most important truths of the faith re-stated during the Second Vatican Council. The Council taught that holiness is the vocation of all the baptized,... All holiness, as the third Eucharistic prayer states, comes from the Father through his son, Jesus Christ, by the working of the Holy Spirit. To be holy is to participate in God’s life through the gift of sanctifying grace.
Extract of Mother Teresa's words in the movie "The Legacy"
"God Speaks in the silence of the heart...and we listen. And then...we speak to God from the fullness of our heart. First we listen...God speaks...and then we speak and God listens. And that connection is prayer...is...oneness with God. A soul of prayer: the fruit of prayer is deepening of Faith, and the fruit of Faith is Love, and the fruit of Love is Service, and the fruit of Service is Peace. That is why we need to pray to have a clean heart...and if we have a clean heart we can see God. And when we can see God naturally we will begin to love one another. That means we see and we look, and then we give our hands to serve and our hearts to love... and that's the beginning of holiness."