Here is Karl Barth reflecting on Martin Luther’s theologia crucis (theology of the cross). Notice towards the end how Barth speaks of the vulnerability of faith before God. This is so key, vulnerability and faith aren’t things often linked together, per se. But I think they go together well; faith denotes trust, and trust denotes recognition of the fact that we are placing our hope and rest somewhere else other than ourselves. We see this exemplified in the life of Christ in the Garden of Gethsemane; i.e. ‘not my will, but thine be done.’ It is important to remain vulnerable before God, before whom we stand naked and bear. Soli Deo Gloria. Here is Barth on Luther:
. . . In contrast Luther tries to draw attention to the vacuum, to the fact that passion (suffering) stands at the heart of life and speaks of sin and folly, death and hell. These fearful visible things of God, his strange work, the crucified Christ — these are the themes of true theology. A preaching of despair? No, of hope! For what does that break in the center mean? Who is the God hidden in the passion with his strange work, and what does he desire? Explaining Heidelberg Thesis 16, Luther pointed out that the strange work leads on to the proper work, that God makes us sinners in order to make us righteous. The gap in the horizontal line, the disaster of our own striving, is the point at which God’s vertical line intersects our lives, where God wills to be gracious. Here where our finitude is recognized is true contact with infinity. He who judges us is he who shows mercy to us, he who slays us is he who makes us live, he who leads us into hell is he who leads us into heaven. Only sinners are righteous, only the sad are blessed, only the dying live. But sinners are righteous, the sad are blessed, the dying do live. The God hidden in the passion is the living God who loves us, sinful, wicked, foolish, and weak as we are, in order to make us righteous, good, wise, and strong. It is because the strange work leads to the proper work that there can be no theology of glory, that we must halt at the sharply severed edges of the broken horizontal line where what we find is despair, humility, the fear of God. For despair is hope, humility is exaltation, fear of God is love of God, and nothing else. The center of this theology, then, is the demand for faith as naked trust that casts itself into the arms of God’s mercy; faith that is the last word that can be humanly said about the possibility of justification before God; a faith that is sure of its object — God — because here there is resolute renunciation of the given character of scholastic faith (infused, implicit, and formed) as an element of uncertainty; faith viewed not as itself a human work but as an integral part of God’s strange work, sharing in the whole paradox of it.
In order to get a better grasp of what Luther’s theology of the cross is about check out his Heidelberg Disputation.
 Karl Barth, The Theology of John Calvin, 46.