The Soul of the Apostolate is one of the most authoritative works on the spiritual life ever written. It lays down the core principles of any type of spirituality in a very neat fashion, quoting Church fathers, saints, doctors of the Church, and the main source of Christian piety, Holy Scripture.
Dom Chautard has laid out the essentials for a truly Christian attitude and execution of the duties necessary for growth in holiness and wisdom. This monumental work stands as one of the pillar works of Christian spirituality and is a must-have for any Christian's library.
A man who is determined to acquire an interior life must take, for his ideal, unremitting domination of self and complete control over his environment, in order to act in all things solely for the glory of God. To achieve this aim, he must strive, under all circumstances, to keep united with Jesus Christ and thus to keep his eye on the end he has in view, and to evaluate everything according to the standard of the Gospel. At prayer, and especially before the Blessed Sacrament, he isolates himself more completely than ever from all visible things, that he may come to converse with the invisible God as if he saw Him. Even in the midst of his apostolic labors he will manage to realize this ideal, which St. Paul admired in Moses. Neither the troubles of life, nor the storms aroused by passion, will succeed in turning him aside from the line of conduct, he has laid down for himself. But on the other hand, if he does weaken for a moment, he pulls himself together at once, and presses forward with even more determination than before.
Love is made perfect by the Eucharist. This living memorial of the Passion revives the divine fire in the soul of the apostle when it seems on the point of going out. It makes him relive Gethsemani, the scene in the Preatorium, Calvary, and teaches him the science of sorrow and humiliation. The apostolic worker will then be able to speak to the afflicted in a language that will make them share the consolations he has drawn from this sublime source.
He speaks the language of the virtues of which Jesus is the only exemplar, because everyone of his words is like a drop of the Eucharistic Blood falling upon souls. But for this reflection of the Eucharistic life the active worker will produce no other effect, by his words, than a passing enthusiasm. It will be merely a matter of captivating the secondary faculties, and occupying the outworks of the fortress. But the stronghold itself, that is the heart, the will, will generally remain impregnable.