It’s difficult–but it doesn’t mean we are sinless. It just means that we have no sins that we are not willing to give up. We all fall now and then, but if we are repentent of our sins, even the most venial, then we are not attached to them.
When we confess a mortal sin, forgiveness is dependent on a firm intention (at that moment ) not to commit that sin again. We all know that it may well be the reality that we will repeat it again, but we at that time of repentance don’t intend to. Similarly we must have that same detachment from venial sin to gain an indulgence. An intention to refrain from repeating them. When it comes to any sin whether mortal or venial unless one is aware that their action or omission is objectively a sin when they commit it is not a sin for which they are culpable.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.