"Observe the difference between the presence of the life-giving spirit and the presence of the spirit that deadens and destroys your soul. When there are good thoughts in your soul you feel happy and at ease; when peace and joy are in your heart, then the spirit of good, the Holy Ghost, is within you; whilst when evil thoughts or evil motions of the heart arise within you, you feel ill at ease and oppressed; when you are inwardly troubled, then the spirit of evil, the crafty spirit, is within you. When the spirit of evil is in us, then, together with oppression of heart and disturbance, we generally feel a difficulty in drawing near to God in our heart, because the evil spirit binds our soul, and will not let it raise itself to God. The evil spirit is a spirit of doubt, unbelief--of passions, oppression, grief and disturbance; whilst the spirit of good is one of undoubting faith, of virtue, of spiritual freedom and breadth--a spirit of peace and joy.
"Know by these tokens when the Spirit of God is within you, and when the spirit of evil, and, as often as possible, raise your grateful heart to the most Holy Spirit that gives you life and light, and flee with all your power from doubt, unbelief, and the passions through which the evil serpent, the thief and destroyer of our souls, creeps in."