Lanteri's life was marked by physical suffering from his pulmonary conditions that restricted his public speaking ability and his poor eyesight, because of which he often sought an assistant to read aloud to him.

[7] With Lanteri he established a close-knit group of laypeople and clergy called the Amicizia Cristiana (Christian Friendship), who worked together to disseminate well-written, edifying books that inspired people to grow in their faith, contribute to society and cope with the unwelcome changes in their lives at the dawn of the French Revolution.

In this series of guided meditations through which one becomes more attentive to the movements of the heart (discernment) and the accompanying rules for adapting them to individuals' particular spiritual needs, Lanteri recognized a powerful instrument for pastoral ministry, especially for conversion.

Lanteri worked to turn the tide of Jansenism, which had become popular in Europe in the preceding centuries and retained many adherents in his time, though formally condemned by the Catholic Church.

[12] Lanteri subsequently promoted Liguorian moral theology, which is based on mercy and hope in contrast with a condemning and rigoristic Jansenism, both personally as he counseled people and young priests and institutionally through various publications.

[13] Scholars such as Guerber have shown that Lanteri, together with Diessbach and their associates in Northern Italy and France, was in large part responsible for the widespread familiarity among clergy with the moral theology of Alphonsus Liguori and its usefulness to both combat Jansenism and accomplish their evangelical mission.