How our sixth combat is against the spirit of accidie, and what its character is.
Our sixth combat is with what the Greeks call ἀκηδία, which we may term weariness or distress of heart. This is akin to dejection, and is especially trying to solitaries, and a dangerous and frequent foe to dwellers in the desert; and especially disturbing to a monk about the sixth hour, like some fever which seizes him at stated times, bringing the burning heat of its attacks on the sick man at usual and regular hours. Lastly, there are some of the elders who declare that this is the “midday demon” spoken of in the ninetieth Psalm.
Source: Institutes (New Advent)