What I am about to say may sound a bit forced, but I mean for it to be taken literally.
When a man plays golf, he has a golf-character, that is, the sum of good and bad habits relevant for playing golf. His golf-flesh is the sum of his bad golf habits. Where do these bad habits reside? They dwell as ingrained tendencies in specific body parts, particular members of the body. His golf game may he weakened by bad habits in the wrists, the shoulders, or somewhere else. He may have good habits in his legs but bad habits, golf-flesh, residing in his shoulders. Golf-flesh resides in the specific members of his body.
How does he develop a good golf-character? Not simply by daily golf-readings coupled with regular exposure to motivational golf-music! No, he must present his members to a golf instructor at a driving range as instruments of golf “righteousness,” instead of following his golf- flesh as an instrument of golf “unrighteousness.” These are not figures of speech. Think of them as literal. By so presenting his members to a wise guide—a golf instructor—he can gradually get rid of bad golf-habits and replace them with good ones.
How does he present his members to a golf instructor? Two things are involved. First, he must dedicate himself to the pursuit of golf righteousness (to getting good at golf), and choose to submit as an apprentice to a master-teacher. Second, he does not simply engage in a one-time act of dedication to the master-teacher. To present his body to a golf instructor requires repeatedly engaging specific body parts in regular activities done over and over again, with the instructor in charge, and practicing different movements. For example, he may present the members of his body—say, the wrists—to the instructor by practicing over and over again a specific wrist movement, a particular swing. The result of such habitual bodily movement will be the replacement of bad habits that dwell in the wrists with good habits. The golf-flesh that resides in the wrists will give way to golf-righteousness in those members. Later the instructor may require the habitual presentation of other members—say, the hips—to replace bad habits that reside there.
A golf-discipline is a repeated golf exercise, a bodily movement involving specific body parts, repeated over and over again. This is done for the purpose of getting rid of golf-flesh and gaining golf-righteousness in the body. Notice that some golf-disciplines are done in practice in a way different from how they are done in the game. Like playing piano scales, they are performed to prepare the player for a different movement than actually takes place in the game. Like scales, the practice activity drops out during the real game (for example, an over-exaggerated swing to compensate for the tendency to hook the ball). Other practice activities are also done in the game (for example, keeping the head down while swinging). But the important thing is this: A golf- discipline is done repeatedly, not to get good at the discipline, but to get good at the game of golf.
The parallels with becoming good at life should be clear. When we present our body to God as a living sacrifice (see Romans 12:1), this involves not just a one-time act of dedication, but a habitual, repeated bodily exercise (see 1 Timothy 4:7-8; 1 Corinthians 9:24-27) involving specific body parts (see Romans 6:12-13,19). This results in putting to death our bad habits (see Colossians 3:5), that is, removing the flesh that resides in those body parts and replacing it with righteousness that comes to reside in the members of our body. A Christian spiritual discipline is a repeated bodily practice, done in dependence on the Holy Spirit and under the direction of Jesus and other wise teachers in His Way, to enable us to get good at certain things in life that we cannot learn to do by direct effort.
— J. P. Moreland, from The Lost Virtue of Happiness, p. 44