The ulcer that sits on a creature's heart

(Andrew Gray "Door Unto Everlasting Life")

Sin is the ulcer that sits on a creature's heart,
and robs him of all true contentment and sound
joy. Oh the secret gnawings that envy, and
pride, and covetousness give a man's soul.

Sin is the soul's disease. It . . .
  blinds the mind,
  hardens the heart,
  enthralls the will,
  defiles the conscience,
  deadens the affections, and
  hurls the whole man into confusion.

Sin brings more evils than either tongue
can speak—or heart can think.