Venial sin, however slight, is always prejudicial to the soul. It weakens our devotion, troubles the peace of our conscience, diminishes the fervour of charity, exhausts the strength of our spiritual life, and obstructs the work of the Holy Ghost in our souls.
I pray you then to do all in your power to avoid these sins, for there is no enemy too weak to harm us if we make no resistance. Slight anger, gluttony, vanity, idle words and thoughts, immoderate laughter, loss of time, too much sleeping, trivial lies or flatteries – such are the sins against which I would particularly warn you. Great vigilance is required against offences of this kind, for occasions of venial sin abound.