The CAPG's Blog
Many priests offer to God their prayers, alms, fasts, and mortifications; but few offer themselves, and make an oblation of their hearts. They always secretly reserve to themselves the disposal of their own will. This division if displeasing to God; it is not the sacrifice of Abel, but of Cain, who offered to God the fruits of the earth, but reserved to himself his heart and will, as St. Augustine says.
Source: The Catholic Priesthood, by Rev. Fr. Michael Muller 1885