I’m reading Sergei Bulgakov’s book on John the Baptist, The Friend of the Bridegroom and colliding, as usual, with my ignorance of Eastern Orthodoxy. So be it.
I made use of what Bulgakov said about the kenosis of God in Trinity and in creation in chapter 2 of The One Story, and kenosis returns when he writes about John the Forerunner of Jesus:

John the Forerunner too is the bearer of humility par excellence and of the most profound self-renunciation. “He must increase, but I must decrease” (John 3:30). . . . [A forerunner] is someone who, renouncing himself, devotes all of himself, all of his life, to another, to someone else, to one who comes after. The Forerunner’s ministry is wholly determined and exhausted by active humility, by self-renouncing love. The Forerunner gives himself wholly to the One who comes, proclaiming: “There cometh one mightier than I after me, the latchet of whose shoes I am not worthy to stoop down and unloose” (Mark 1:7). To give one’s life for the Other, to devote oneself wholly to the One who comes, to lose one’s I in voluntary, sacrificial self-annulment — that is the feat of love that, in a spirit of humility, humbles itself as much as it is humanly possible. . . . “The friend of the bridegroom . . . rejoiceth greatly because of the bridegroom’s voice: this my joy therefore is fulfilled” (John 3:29). (p. 3)

This is not just the kenosis of discipleship (as in chapter 10 of The One Story)—or better, it simply isn’t the kenosis of discipleship. It is, rather, the kenosis of one who submits to a unique and irreducible role in God’s plan for our salvation. The self-promotion that we encourage and applaud in each other (see my post on Obscurity) is lost in John’s submission to his mission of pointing to another. In this humility he is like Mary the mother of Jesus (Luke 1:38) and like Jesus himself (Luke 22:42; The Friend of the Bridegroom, pp. 11–12).
But the uses of Mary, John, and Jesus as models for humble discipleship are clear enough. But, on the other hand (I’m starting to sound like Tevye the milkman), they could just encourage the foolishness so many of us engage in of thinking “I, too, have a unique role that I alone am called to,” which would be to miss out on what the Forerunner is about.

• Sergei Bulgakov,The Friend of the Bridegroom: On the Orthodox Veneration of the Forerunner (Eerdmans, 2003) (Google Books link).