What is the "universal call to holiness"?
Vatican II states in Paragraphs 39-42 of LUMEN GENTIUM, that all members of the Church are called to holiness. In other words, we are ALL called to be great saints!
The Bible even mentions the importance of holiness. Here are some examples from Scripture:
In Revelation 3:15 -16, God tells us that He despises a lukewarm heart, telling us that we can never be spiritually neutral towards Him, making us choose to either be for Him or against Him.
In Jas 1:19-27, St. James tells us that our life must reveal Jesus to the world. In other words, St. James is emphasizing the universal call to holiness.
In 1 Cor 11:27-32, St. Paul emphasizes the importance of receiving the Eucharist in the state of grace, basically telling Catholics to always be holy when receiving the Blessed Sacrament.
In Matthew 5:23-24, Jesus emphasizes the importance of not having hostility in your heart towards your fellow man. Jesus basically wants us to approach the altar with a love directed towards Him, and to mankind. St. Matthew beautifully shows us the universal call to holiness in this chapter.
With these scriptural examples, we can see the importance of being holy. To understand the importance of receiving the Eucharist in a state of grace, read the following:
Paragraphs 36-37 of ECCLESIA DE EUCHARISTIA by Pope John Paul II
The Eucharist and Penance by Alfredo Marranzini
Paragraphs 81-82 of REDEMPTOR HOMINIS by Pope John Paul II
Finally, we need to remember to go to frequent Confession, so that we may always faithfully live out the universal call to holiness. For information about the Sacrament of Penance and Reconciliation; and to learn how to properly confess your sins to Jesus in the priesthood, check out the following:
Sacrament of Penance: Examination of Conscience by Father John Trigilio
THE SACRAMENT OF PENANCE AND RECONCILIATION (Catechism of the Catholic Church 1422-1498)
Pastoral Letter: God's Mercy and the Sacrament of Penance by Archbishop Wuerl
"God's Gift of Forgiveness: The Pastoral Exhortation on the Sacrament of Penance and Reconciliation"