In Keeping the Heart, John Flavel (1627-1691) centers his teaching on Proverbs 4:23: "Keep your heart with all vigilance, for from it flow the springs of life." Flavel maintains that it is our great responsibility as Christians to watch our hearts and guard them against sin and lifelessness in spiritual duties. This watchfulness also results in a more joyful and victorious life that adorns the Gospel with beauty. The main part of the book provides advice on how to approach various seasons of life that each pose their own dangers to the heart.

This book was first published in 1670 as "A Saint Indeed, or The Great Work of a Christian in Keeping the Heart in the Several Conditions of Life." This edition attempts to make Flavel's writing more accessible to modern readers. It includes the following updates:

• Complete and carefully updated text.
• Sentence-level rewriting and rewording for clarity.
• Modern English sentence structure.
• Modern English vocabulary.
• Updated organization and headings.
• English Standard Version (ESV) scripture references.
• Scripture quotations in footnotes.
• Active table of contents.