"The demons cunningly withdraw for a time in the hope that we will cease to guard our heart, thinking we have now attained peace; then they suddenly attack our unhappy soul and seize it like a sparrow. Gaining possession of it, they drag it down mercilessly into all kinds of sin, worse than those which we have already committed and for which we have asked forgiveness. Let us stand, therefore, with fear of God and keep guard over our heart, practicing the virtues which check the wickedness of our enemies."
- Saint Isaiah the Solitary
Reference: Philokalia: Volume 1