Striving for holiness, we are still sinful

"It is appropriate that... the Church should become more fully conscious of the sinfulness of her children, recalling all those times in history when they departed from the spirit of Christ and his Gospel and, instead of offering to the world the witness of a life inspired by the values of faith, indulged in ways of thinking and acting which were truly forms of counter-witness and scandal.

"Although she is holy because of her incorporation into Christ, the Church does not tire of doing penance: before God and man she always acknowledges as her own her sinful sons and daughters. As Lumen Gentium affirms: 'The Church, embracing sinners to her bosom, is at the same time holy and always in need of being purified, and incessantly pursues the path of penance and renewal.'

".... (The Church) cannot cross the threshold of the new millennium without encouraging her children to purify themselves, through repentance, of past errors and instances of infidelity, inconsistency, and slowness to act. Acknowledging the weaknesses of the past is an act of honesty and courage which helps us to strengthen our faith, which alerts us to face today's temptations and challenges and prepares us to meet them."

John Paul II
Apostolic Letter, Tertio Millennio Adveniente, 33 (1994)