By God's grace we do the best we can. But also keep in mind the distinction between mortal and venial sin. Only that latter separates us from God. (I know that you do not accept this distinction but it is an important one.) And if one were to commit a mortal sin, all he would have to do is repent and seek forgiveness in confession. See, a pure gift and not something that I "earn" through works.
I guess Rome gets to choose 'sin' falls into what bracket - right?
Matthew 5:17-20 Douay-Rheims Bible
Jesus Fulfills the Law
17 Do not think that I am come to destroy the law, or the prophets. I am not come to destroy, but to fulfill. 18 For amen I say unto you, till heaven and earth pass, one jot, or one tittle shall not pass of the law, till all be fulfilled. 19 He therefore that shall break one of these least commandments, and shall so teach men, shall be called the least in the kingdom of heaven. But he that shall do and teach, he shall be called great in the kingdom of heaven.
20 For I tell you, that unless your justice abound more than that of the scribes and Pharisees, you shall not enter into the kingdom of heaven.
Does the 'least' fall into the moral or venial class?