[4] According to the Catechism of the Catholic Church: 1862 One commits venial sin when, in a less serious matter, he does not observe the standard prescribed by the moral law, or when he disobeys the moral law in a grave matter, but without full knowledge or without complete consent.
Intentional ignorance and "hardness of heart" increase "the voluntary character of a sin".
Penance left undone during life contributes to the purifying process one must undergo while in the state of Purgatory.
One receives from the sacrament of reconciliation the grace to help overcome venial, as well as mortal sins.
[citation needed] Catholics believe that followers should not take venial sin lightly, especially when committed deliberately.
No one without a special grace (generally taken to apply only to the Virgin Mary) can avoid even semi-deliberate venial sins entirely (according to the definition of Trent).
In the case of the believers those sins are called mortal which force the Holy Spirit to depart from one's heart, which destroy faith.