Why do Christians mourn over sin?

Christian mourning over sin is rooted in understanding the gravity of our disobedience towards God and the cost it brought upon Christ. In Zechariah 12:10, it states that they shall mourn for Him as one mourns for an only son. This mourning is not merely a sorrow for consequences but a deep recognition that our sins contributed to the suffering of Christ. When we truly comprehend that 'it was our sins that nailed Him to the cross,' as noted in the words of Isaac Watts, it deeply impacts our hearts. Such mourning drives us to repentance and increases our appreciation for God's mercy and grace through Christ's sacrifice.