This in turn exposes the soul to every attack of the enemy. Sin makes the person blind, obstinate, and proud. It teaches the self to depend on its own strength. It cautions against dealing with desires that go beyond its strength. It reminds the self of the many misfortunes and hurt it experienced, every time it trusted others.
Sin is like a virus that keeps hiding itself.
The effect is negligible and it influences every thought and desire. Lack of gratitude and a habit of becoming careless in little things, leads to lack of vigilance. The vigilant soul is careful to notice the virus or at least the infection that sin causes. Carelessness leaves the virus to destroy the built in reserves of all the virtues. The soul becomes weak and the light of faith becomes dim because the oil of faith seems to run out.