Nicene and Post-Nicene Fathers: Series II/Volume XI/John Cassian/The Twelve Books/Book XII/Chapter 16
Chapter XVI.
That we cannot even make the effort to obtain perfection without the mercy and inspiration of God.
We ought therefore, in accordance with their teaching and instruction, so to press towards it, and to be diligent in fastings, vigils, prayers, and contrition of heart and body, for fear lest all these things should be rendered useless by an attack of this malady. For we ought to believe not merely that we cannot secure this actual perfection by our own efforts and exertions, but also that we cannot perform those things which we practise for its sake, viz., our efforts and exertions and desires, without the assistance of the divine protection, and the grace of His inspiration, chastisement, and exhortation, which He ordinarily sheds abroad in our hearts either through the instrumentality of another, or in His own person coming to visit us.