The modern manuals, which focused on norm ethics, moral law, and conscience, was different from the Thomistic tradition, which focused on prudence. Both law and conscience aren't sufficient to develop the theology of love and morals expressed toward our end. We need the virtues to act well with consistency. The virtues in Saint Thomas form a composite whole, and the dynamism of grace works within them, with charity ordering them all to God.
Prudence governs every action, and judges all of the virtues, including the theological ones.
There is no limit to our love, faith, and hope, but in the way we express these virtues must be governed by prudence. Prudence discerns here and now what is to be done. Prudence uses all the knowledge of moral science, including synderesis, to make its decision. Saint Thomas says the judgment of conscience remains at the level of knowledge, but the free choice involves the will. Prudence doesn't limit itself to the deliberation in the abstract, but culminates in the command.