Spiritual formation is a process of being conformed to the image of Christ for the sake of others…[It] is a loving relationship with God that shapes our being rather than a technique or method or program for self-improvement. –M. Robert Mulholland Jr.
Spiritual formation in the tradition of Jesus Christ is the process of transformation of the inmost dimension of the human being, the heart, which is the same as the spirit or will. It is being formed (really, transformed) in such a way that its natural expression comes to be the deeds of Christ done in the power of Christ. –Dallas Willard
Spiritual Formation: What it is, and How it is Done (Dallas Willard)
What is spiritual formation? (Renovaré)