The one marvelous secret of a holy life lies not in imitating Jesus, but in letting the perfections of Jesus manifest themselves in my mortal flesh.
Sanctification is "Christ in you."
It is His wonderful life that is imparted by faith as a sovereign gift of God's grace.
How can I say it better then that? Good ol' Chambers. We received his devotional My Utmost for His Highest for our wedding and we love reading it together. It's worth checking out!