Believe me, brother, that boredom, accidie, sluggishness, irritation, mental fatigue and the other causes of distress that the enemy of righteousness inflicts upon ascetics, are all with divine permission. If man puts up with them patiently and without buckling, they will be rendered to him as a pure oblation and a holy accomplishment—provided he is free from pride and vanity.

—St Isaac the Syrian, in “The Four Books,” 1.5.92—94