Don Carson has written helpful of the danger of not keeping the gospel central as we pursue the Spiritual Disciplines, I ran out of space to include it in my sermon, so please read it here.  

“The gospel is not a minor theme that deals with the point of entry into the Christian way, to be followed by a lot of material that actually brings about the life transformation…Preaching the gospel, it is argued, is announcing how to be saved from God’s condemnation; believing the gospel guarantees you won’t go to hell. But for actual transformation to take place, you need to take a lot of discipleship courses, spiritual enrichment courses, “Go deep” spiritual disciplines courses, and the like. You need to learn journaling, or asceticism, or the simple lifestyle, or Scripture memorization; you need to join a small group, an accountability group, or . . . Bible study.

Not for a moment would I speak against the potential for good of all of these steps; rather, I am speaking against the tendency to treat these as postgospel disciplines, disciplines divorced from what God has done in Christ Jesus in the gospel of the crucified and resurrected Lord. . . .

Failure to see this point has huge and deleterious consequences. . . . First, if the gospel becomes that by which we slip into the kingdom, but all the business of transformation turns on postgospel disciplines and strategies, then we shall constantly be directing the attention of people away from the gospel, away from the cross and resurrection. Soon the gospel will be something that we quietly assume is necessary for salvation, but not what we are excited about, not what we are preaching, not the power of God. What is really important are the spiritual disciplines.

Of course, when we point this out to someone for whom techniques and disciplines are of paramount importance, there is likely to be instant indignation. Of course I believe in the cross and resurrection of Jesus, they say. And doubtless they do. Yet the question remains: What are they excited about? Where do they rest their confidence? On what does their hope of transformation depend? When I read, say, Julian of Norwich, I find an example of just how far an alleged spirituality may be pursued, in medieval form, directly attempting to connect with God apart from self-conscious dependence on the substitutionary death and resurrection of Jesus—the very matters the apostle labels “of first importance.” Wherever contemporary pursuit of spirituality becomes similarly distanced from the gospel, it is taking a dangerous turn”

D. A. Carson, "What Is the Gospel?-Revisited," in For the Fame of God's Name: Essays in Honor of John Piper (Wheaton, IL: Crossway, 2010), 164-165

P.S. Another quote I left out on Sunday….Trevin Wax at the Gospel Coalition has written a similar warning:

“In the spiritual formation wave, it’s far too easy for the gospel to be assumed instead of explicit, for Scripture to take a backseat to experience, and for the church to become a sideshow to one’s individual journey.”