This is correct to the extent that it’s properly understood. What is meant by “the state of our soul”? Justice in man isn’t comprised merely of a sort of austere self-denial, abstinence from sin, as if we’ll be saved as long as we can just somehow skate along until death without falling into serious sin. Justice for man-God’s expectation for us- has an extremely positive note, having to do with the changes and transformation God desires to effect in us, changes that preclude sin by their nature. From the CCC:
1991 Justification is at the same time the acceptance of God’s righteousness through faith in Jesus Christ. Righteousness (or “justice”) here means the rectitude of divine love. With justification, faith, hope, and charity are poured into our hearts, and obedience to the divine will is granted us.
Here’s another, ending with a famous quote by St John of the Cross:
1022 Each man receives his eternal retribution in his immortal soul at the very moment of his death, in a particular judgment that refers his life to Christ: either entrance into the blessedness of heaven-through a purification or immediately, – or immediate and everlasting damnation.
“At the evening of life, we shall be judged on our love.”
Mortal sin is sort of the flip-side of love. Mortal sin opposes and destroys love of God and neighbor in us:
**1856 Mortal sin, by attacking the vital principle within us - that is, charity - necessitates a new initiative of God’s mercy and a conversion of heart which is normally accomplished within the setting of the sacrament of reconciliation:
When the will sets itself upon something that is of its nature incompatible with the charity that orients man toward his ultimate end, then the sin is mortal by its very object . . . whether it contradicts the love of God, such as blasphemy or perjury, or the love of neighbor, such as homicide or adultery. . . . But when the sinner’s will is set upon something that of its nature involves a disorder, but is not opposed to the love of God and neighbor, such as thoughtless chatter or immoderate laughter and the like, such sins are venial.
1855 Mortal sin destroys charity in the heart of man by a grave violation of God’s law; it turns man away from God, who is his ultimate end and his beatitude, by preferring an inferior good to him.
Venial sin allows charity to subsist, even though it offends and wounds it.
1861 Mortal sin is a radical possibility of human freedom, as is love itself. It results in the loss of charity and the privation of sanctifying grace, that is, of the state of grace. If it is not redeemed by repentance and God’s forgiveness, it causes exclusion from Christ’s kingdom and the eternal death of hell, for our freedom has the power to make choices for ever, with no turning back. However, although we can judge that an act is in itself a grave offense, we must entrust judgment of persons to the justice and mercy of God.**
People don’t always understand that love isn’t a sort of side note to the gospel and our faith; it’s the very core of it. We can refrain from sin while not yet having attained to true justice. Mortal sin however, is a complete turning away from justice, from love, from God.