Spiritual Formation is often talked about in terms of how it is accomplished. This means that when the conversation turns to formation it generally rotates on the fulcrum of how one becomes or pursues formation.
Most of the time SF is talked about in terms of the kinds of disciplines one practices in order to be formed – inward disciplines, outward disciplines, corporate disciplines, disciplines of engagement, disciplines of abstinence are all ways we seek to describe what it means to pursue Christ likeness and grow in Him.
One of the more helpful ways to approach this topic of spiritual formation is to think of it, as Dr. Richard Averbeck does, using the metaphor of spiritual breathing. Listen to what he says in a lecture on the practice of spiritual formation:
“This connection with the fact that the word “spirit” in the Old and New Testament can mean breathe and breathing, just as much as spiritual can mean wind and breath…(therefore) I think that dividing the spiritual disciplines into two categories corresponding to human breathing is a good way to go about trying to understand (spiritual formation)…no one can live without breathing, and breathing involves alternately inhaling and exhaling. The spiritual disciplines are about…inhaling and exhaling with the life giving dynamic relationship between them.” (Christian University GlobalNet, SF 507: Foundations of Spiritual Formation 1, Lecture #3)
There is a dynamic tension here between the necessity of taking in and giving out. Both feeding and serving are necessary if we are to be formed spiritually.
The idea here is akin too but not completely the same as the put on and put off instruction given by the apostle Paul in Ephesians 4.
So I tell you this, and insist on it in the Lord, that you must no longer live as the Gentiles do, in the futility of their thinking. They are darkened in their understanding and separated from the life of God because of the ignorance that is in them due to the hardening of their hearts. Having lost all sensitivity, they have given themselves over to sensuality so as to indulge in every kind of impurity, with a continual lust for more. 
 The Holy Bible: New International Version. 1996 (electronic ed.) (Eph 4:17–19). Grand Rapids, MI: Zondervan.