My dearest daughter in Christ: you desire to follow the height of perfection. Drawing near your God, you wish to become one spirit with him (1 Cor 6.17). As this is the greatest and noblest undertaking that one can describe or imagine, you must first come to know what makes for the true and prefect spiritual life.
Indeed many, without much reflection, have placed it in a rigorous life of mortifying the flesh: in hair shirts, flagellation, lengthy vigils, fasting, and other similarly harsh and tiresome bodily acts. Others, and in particular women, believe themselves to have progressed greatly if they recite many vocal prayers, if they hear many masses and long Psalmody, if they frequently attend church and have recourse to the Eucharistic banquet. Many others have persuaded themselves that perfection depends above all else on frequenting choir, on silence, on solitude and on regulated discipline: so that some people hold that perfection is founded in these actions, while others hold it to be founded in other, similar actions. (Among these we find at times those who, dressed in a religious habit, live in the cloister.) Not so! Inasmuch as said actions are initially a means of acquiring spirit and later the fruit of the spirit, it cannot be said that Christian perfection and the true spirit consists in these pursuits alone. Beyond a doubt, they are a very powerful tool. They allow who use them carefully and with discretion to acquire the spirit, to acquire vigor and strength against one’s own malice and fragility; to arm oneself against the assaults and deceptions of our communal enemy; to provide oneself with those spiritual helps that are necessary to all God’s servants and especially to beginners. They are later the fruit of the spirit of truly spiritual people, who castigate their flesh because it has offended its Creator, and to hold it submissive and humble in his service. They keep quiet and live solitary lives, fleeing whatever small offense they might give the Lord and conversing with the heavens (Phil. 3.20 Vulg). They attend to divine worship and works of piety; they pray and meditate on the life and passion of our Lord — not out of curiosity and sensory delights, but to come to know better their own malice and the merciful goodness of God. By this knowledge they inflame themselves all the more with divine love and hatred of self, following the Son of God by denying themselves and taking up their cross. They frequent the most holy sacraments for the glory of his divine Majesty, to join themselves more closely to God and to draw new strength against their foes. But for those who build all their foundation from the aforesaid external works, they can become instead the occasion for worse ruin than an openly-committed sin! This is due not to any defect in the works themselves (for they are all most holy) but to the defect in the one who makes use of them. Focused only with these external acts, they abandon their hearts in the hands of their inclinations and to the hidden demon. The latter, seeing that they are already off the right path, not only allows them to continue with delight in the aforesaid exercises, but also to range among the delights of paradise according to their vain thoughts, where they persuade themselves to have been raised up among angelic choirs and to hear God inside themselves. They find themselves so completely absorbed in certain meditations full of high, curious and delightful matters that, almost forgetting the world and its creatures, they fancy themselves to be rapt into the third heaven. One can easily comprehend from their habits how numerous are the errors in which they entangle themselves, and how far they are from the perfection we seek. Indeed, in everything, be it great or minor, they desire preference and advantage. They are stubborn in their personal opinions and obstinate in their will. Blind to themselves, they are instead solicitous and diligent observers and gossips of the sayings and actions of others. They hold to a vain reputation and enjoy being held in that reputation by others. Should you touch it in even the smallest way, and you take away those devotions that they use passively, they change completely and grow troubled. Even if God should send them difficulties and illness, or allow some persecution to befall them — for such things never come against his will, but either by his desiring them or allowing them in order to make people truly aware of themselves and of the road of perfection, and are the sure measure of comparison with his true servants — then they discover their false foundation and the internal corruption and wreckage caused by their pride. In fact in every happening, be it sad or happy, they do not want to resign and humble themselves under the hand of God, contenting themselves in God’s ever just — if secret — judgments (Rom 11.33). Nor do they follow the example of his Son, who humbled himself and wished to suffer (Phil. 2.8), by submitting themselves to all creatures, considering their persecutors to be their very friends, effectively the instruments of divine goodness, cooperating in their own mortification, perfection and salvation. Thus it is a certainty that such people are in grave danger: their inner eye darkened, they use it to marvel at external actions that are good, and attribute to themselves many degrees of perfection. Thus made proud, they judge others; but none can convert them, apart from some extraordinary help from God. For these reasons does a public sinner convert himself and become good far more easily than the sinner whose sin is hidden and covered by the mantle of apparent virtue. You see clearly that, daughter, that as I have said, the spiritual life does not consist in the aforesaid things.