The challenge with the whole area of studying spirituality and spiritual formation is that for decades, the Roman Catholics have dominated this area of study. While Evangelicals poured in tremendous resources preaching the gospel and responding to liberal theology and modernity (all of which needed to be done, no doubt about that), Roman Catholic theologians developed a whole area of what they would call spiritual theology. Now, Evangelicals are playing catch up and so frequently do not have the depth of thought on the subject. And given our ecclesial climate (ECT e.g.), it is all too easy to see the Roman Catholics as the masters at whose feet we need to sit. It is almost as if Evangelicals are saying: if you want to learn about how to be saved come to us. But then, on how to live the Christian life, you need to learn from the Roman Catholics. This is a vast over-simplification, but explains a little why Roman Catholic devotional practices are so easily assimilated into Evangelical piety.
But this is deeply problematic, for the theological foundation upon which Roman Catholics do spiritual formation is skewed (the Reformation was not a mistake and is still needful to orient our thinking). So there needs to be laid—which is what our Puritan forebears did—a solid theological foundation, from which proper reflection on piety can be done. And here Puritan methodology surely points the way. This does not mean that the Roman Catholics have nothing to teach us, but whatever is appropriated must be in line with biblical foundations.