This is a Catholic teaching that is explained beautifully in Chapter 5 of the Church's Second Vatican Council document, Lumen Gentium, from which the following excerpts are taken:

#39. "Therefore in the Church, everyone whether belonging to the hierarchy, or being cared for by it, is called to holiness, according to the saying of the Apostle: 'This is the will of God, your [holiness].'" (1 Thessalonians 4:3)

#40. "The Lord Jesus, the divine Teacher and Model of all perfection, preached holiness of life to each and everyone of His disciples of every condition. He Himself stands as the author and consumator of this holiness of life: 'Be you therefore perfect, even as your heavenly Father is perfect.'" (Matthew 5:48)

#42, §1. "Each one of the faithful must willingly hear the Word of God and accept His Will, and must complete what God has begun by their own actions with the help of God's grace. These actions consist in the use of the sacraments and in a special way the Eucharist, frequent participation in the sacred action of the Liturgy, application of oneself to prayer, self-abnegation, lively fraternal service and the constant exercise of all the virtues."

#42, §5. "Therefore, all the faithful of Christ are invited to strive for the holiness and perfection of their own proper state [in life]. Indeed they have an obligation to so strive. Let all then have care that they guide aright their own deepest sentiments of soul. Let neither the use of the things of this world nor attachment to riches, which is against the spirit of evangelical poverty, hinder them in their quest for perfect love. Let them heed the admonition of the Apostle to those who use this world; let them not come to terms with this world; for this world, as we see it, is passing away." (1 Corinthians 7:31)