We all know that exercise is good for the health, and that regular employment of our muscles and limbs promotes our bodily comfort, and increases our bodily vigor.
Now that which exercise does for our bodies, zeal will do for our souls. It will help mightily to promote inward feelings of joy, peace, comfort, and happiness.
None have so much enjoyment of Christ as those who are ever zealous for His glory—jealous over their own walk—tender over their own consciences—full of anxiety about the souls of others—and ever watching, working, laboring, striving, and toiling to extend the knowledge of Jesus Christ upon earth. Such people live in the full light of the sun, and therefore their hearts are always warm. Such people water others, and therefore they are watered themselves.
~ J.C. Ryle
Practical Religion, “Zeal”, [Carlisle, PA: Banner of Truth, 1998], 198.