The Institutes, Book 10
The Sixth Combat: Acedia
Our sixth combat is with what the Greeks call acedia, which we may call weariness or distress of heart. It is close kin to dejection. It is especially hard on those who live alone, and a dangerous and frequent enemy of those who live in the desert. It troubles a monk most around the sixth hour, like a fever that seizes him at set times and brings the burning heat of its attacks on the sick man at his usual, regular hours. Indeed, some of the elders declare that this is the “midday demon” spoken of in the ninetieth Psalm.