St. Francis de Sales always developed his points with thorough examples and images.
In his sermon for Ash Wednesday( previously posted) he explained the three principles or conditions for fasting. One of those was never to fast through vanity but always through humility.
St. Francis de Sales explains: “To fast through vanity is to fast through self-will. It is to fast as one wishes and not as others wish; to fast in the manner which pleases us, and not as we are ordered or counseled. You will find some who wish to fast more than is necessary, and others who do not wish to fast as much as is necessary. What causes that except vanity and self-will? All that proceeds from us seems better to us, and is much more pleasant and easy for us than what is enjoined on us by another.
Do not allow your fast to resemble that of hypocrites, who wear melancholy faces and who consider holy only those who are emaciated. What folly! As if holiness consisted in being thin! Certainly St. Thomas Aquinas was not thin; he was very stout. And yet he was holy. In the same way there are many others, who, though not thin, nevertheless fail not to be very austere and excellent servants of God.
Consider the human spirit: it takes account only of appearance, and being vain, does its works to be seen by others. Our Lord tells you not to do as they do but let your fast be done in secret, only for the eyes of your heavenly Father, and He will see you and reward you.”
Reflection:
How much of the human spirit remains in my fasting this Lent?
What resolve can I make to do all for God?
Source: Sermon for Ash Wednesday, 1622