When our Lord and Master Jesus Christ said, "Repent" (Mt 4:17), he willed the entire life of believers to be one of repentance. Martin Luther, Theses # 1 of his 95 Theses.
"What do you think? A man had two sons; and he went to the first and said, 'Son, go and work in the vineyard today.' And he answered, 'I will not'; but afterward he repented and went. And he went to the second and said the same; and he answered, 'I go, sir,' but did not go. Which of the two did the will of his father?" Matthew 21:28–31 (RSV)
What a treasure do we have in repentance! We acknowledge that we have sinned against the Father in thought, word, and deed. Our souls know holy grief and sorrow over our sin, not in misery or shame, but freeing truth.
A Christian is honest about themselves, not pretending that we do not sin, or if we do, our sin is a small matter. Repentance will not allow us to act as if we have a right to stand in God's presence. We come before the Father seeking the mercy we do not deserve, trusting in His Grace alone.
What of the sin of those around us? Yes, we will not pretend that they have not sinned. We will not go the way of the world, excusing sin as some form of personal freedom or living out 'my truth.' It is suitable to admonish them, keeping before our eyes the sins that cling closely to us.
The Father's will is that we learn to let go of this world so we might be prepared to live in the new world to come through repentance.