Whenever in your path you find unchanging peace, beware: you are very far from the divine paths trodden by the weary feet of the saints. For as long as you are journeying in the way to the city of the Kingdom and are drawing nigh to the city of God, this will be a sign for you: the strength of the temptations that you encounter. And the nearer you draw nigh and progress, the more temptations will multiply against you. Whenever, therefore, you perceive in your soul diverse and stronger temptations in your path, know that at that time your soul has in fact secretly entered a new and higher level, and that grace has been added to her in the state wherein she was found; for God leads the soul into the afflictions of trials in exact proportion to the magnitude of the grace He bestows.

The Ascetical Homilies of Saint Isaac the Syrian, translated by the Holy Transfiguration Monastery, Boston, 1984. 208.