Next to the Bible, A Treatise on Keeping the Heart, sometimes known as A Saint Indeed-The Great Work of a Christian, by the Rev. John Flavel, may be the most wonderful book I have ever read. It is, however, difficult to read in its original version because of its somewhat archaic linguistic style (the original was penned by Flavel in 1667). For that reason, I have modernized the language and modified some parts in this edition for the sake of clarification...