Passion for God is not lost overnight. It is a slow imperceptible drift. Often not even intentional. You wake up one day and 1) Know something is wrong; "See the heights from which you have fallen." 2) The Spirit speaks. "Go back" (repent). You know He's right, so 3) You surrender to "do what you did when first you fell in love." (Rev 2:5) Sweet restoration from those times of drifting is one surrendered moment away.
