If any one saith, that men are justified, either by the sole imputation of the justice of Christ, or by the sole remission of sins, to the exclusion of the grace and the charity which is poured forth in their hearts by the Holy Ghost, and is inherent in them; or even that the grace, whereby we are justified, is only the favour of God; let him be anathema.
The first error seems to be related to what was said in §10:
If any one saith,…that it is by [Christ’s] justice itself that [men] are formally just; let him be anathema.
It is not the case that justification consists solely in the imputation of Christ's justice, nor solely in remission of sins. Justification is not a legal fiction. Rather, as the canon says, the grace and charity of the Holy Spirit are poured into our hearts, and become inherent in us: we are made holy, not simply made not guilty.
Note again that this infusion of grace and charity is something that God does: we do not make ourselves holy. We do not make ourselves just. It is the work of God.