If you're looking for a master in the spiritual life who writes in a down-to-earth, understandable format, then St. Francis de Sales is your guide. It is remarkable that a priest with so many demands as St. Francis could write countless letters and treatises, but one could say this is how his apostolate reached more people. To this day, men and women in all states of life are benefiting from his invaluable advice and direction.
It is hard to pick a favorite work from a favorite author, but I really drew much from St. Francis' Introduction to the Devout Life. Perhaps because it is so varied in the practical sense....one could literally find advice about most any situation and how to grow in virtue. From the Sacraments, to meditations, to virtues and vices, to friendship, St. Francis has an encouraging word to say on every topic. His words are truly immortal because they are just as relevant today as when he wrote them.
One great quote from this work is about choosing to be "in the world" but not "of it" and adhering strongly to our devotion to God: "Never heed this blind world, then; let it cry out as it will, like a bat that would disturb the birds of day. Let us be firm in our plans, unchanging in our resolutions; perseverance will show whether we are in earnest in offering ourselves to God and leading a devout life. . . . Hypocrisy and true virtue have a considerable external resemblance, but they are easily distinguished, since hypocrisy does not endure, but soon vanishes like the rising smoke, whilst true virtue abides firm and constant. . . . We are crucified to the world, and the world should be crucified to us. It counts us as fools, let us count its votaries as madmen."
Other inspiring works of his include: Roses Among Thorns, The Sign of the Cross, The Art of Loving God, Consoling Thoughts (4 parts), Serenity of Heart, his Sermons, Treatise on the Love of God, and so many more! St. Francis de Sales is one of my favorite saints because he devoted so much time to writing as a way to really reach souls. People drew profit from his advice because it made the attainment of holiness seem possible. His life was a model of virtue and sacrifice, one example being his tireless efforts to convert the Calvinists resulting in nearly 60,000 people returning to the Catholic Faith. His last word of advice before his death was "humility."
One could write forever about the glories of this amazing saint. He is an ideal saint to pray to because one can tell by his writings how understanding he was of human nature--thus giving him the name of "gentle saint." St. Francis knew above all how to encourage souls in the pursuit of Heaven by carrying our daily crosses for the love of God. Take the time to read one (or many!) of his excellent works. It is well worth it! St. Francis de Sales, pray for us.