from the INTERIOR CASTLE...ST. THERESE OF AVILA

SOUL IN MORTAL SIN

1. BEFORE going farther, I wish you to consider the state to which mortal sin brings this magnificent and beautiful castle, this pearl of the East, this tree of life, planted beside the living waters of life which symbolize God Himself. No night can be so dark, no gloom nor blackness can compare to its obscurity. Suffice it to say that the sun in the centre of the soul, which gave it such splendour and beauty, is totally eclipsed, though the spirit is as fitted to enjoy God's presence as is the crystal to reflect the sun.
2. While the soul is in mortal sin nothing can profit it; none of its good works merit an eternal reward, since they do not proceed from God as their first principle, and by Him alone is our virtue real virtue. The soul separated from Him is no longer pleasing in His eyes, because by committing a mortal sin, instead of seeking to please God, it prefers to gratify the devil, the prince of darkness, and so comes to share his blackness. I knew a person to whom our Lord revealed the result of a mortal sin  and who said she thought no one who realized its effects could ever commit it, but would suffer unimaginable torments to avoid it. This vision made her very desirous for all to grasp this truth, therefore I beg you, my daughters, to pray fervently to God for sinners, who live in blindness and do deeds of darkness.
3. In a state of grace the soul is like a well of limpid water, from which flow only streams of clearest crystal. Its works are pleasing both to God and man, rising from the River of Life, beside which it is rooted like a tree. Otherwise it would produce neither leaves nor fruit, for the waters of grace
nourish it, keep it from withering from drought, and cause it to bring forth good fruit. But the soul by sinning withdraws from this stream of life, and growing beside a black and fetid pool, can produce nothing but disgusting and unwholesome fruit.
Notice that it is not the fountain and the brilliant sun which lose their splendour and beauty, for they are placed in the very centre of the soul and cannot be deprived of their lustre. The soul is like a crystal in the sunshine over which a thick black cloth has been thrown, so that however brightly the sun may shine the crystal can never reflect it.