St. John Climacus: On Unmanly Fears

"My hair and my flesh shuddered" (Job 4:15). These were the words of Eliphaz when he was talking about the cunning of this demon. Fear starts sometimes in the soul, sometimes in the body, and the one communicates the weakness to the other. But if your soul is unafraid even when the body is terrified, you are close to being healed. However, it is barreness of soul, not the darkness or the emptiness of places, which gives the demons power against us. And the providence of God sometimes allows this to happen so that we may learn from it.  

(The Ladder of Divine Ascent)