If, as was said before, you cannot believe, you must entreat God for faith. This too rests entirely in the hands of God. What we said about suffering also applies here, namely, that sometimes faith is granted openly, sometimes in secret.
However, you can spur yourself on to believe. First of all, you must no longer contemplate the suffering of Christ (for this has already done its work and terrified you), but pass beyond that and see his friendly heart and how this heart beats with such love for you that it impels him to bear with pain your conscience and your sin. Then your heart will be filled with love for him, and the confidence of your faith will be strengthened. Now continue and rise beyond Christ’s heart to God’s heart and you will see that Christ would not have shown this love for you if God in his eternal love had not wanted this, for Christ’s love for you is due to his obedience to God. Thus you will find the divine and kind paternal heart, and, as Christ says, you will be drawn to the Father through him. Then you will understand the words of Christ, “For God so loved the world that he gave his only Son, etc.” [John 3:16]. We know God aright when we grasp him not in his might or wisdom (for then he proves terrifying), but in his kindness and love. Then faith and confidence are able to exist, and then man is truly born anew in God.
15. After your heart has thus become firm in Christ, and love, not fear of pain, has made you a foe of sin, then Christ’s passion must from that day on become a pattern for your entire life. Henceforth you will have to see his passion differently. Until now we regarded it as a sacrament which is active in us while we are passive, but now we find that we too must be active, namely, in the following. If pain or sickness afflicts you, consider how paltry this is in comparison with the thorny crown and the nails of Christ. If you are obliged to do or to refrain from doing things against your wishes, ponder how Christ was bound and captured and led hither and yon. If you are beset by pride, see how your Lord was mocked and ridiculed along with criminals. If unchastity and lust assail you, remember how ruthlessly Christ’s tender flesh was scourged, pierced, and beaten. If hatred, envy, and vindictiveness beset you, recall that Christ, who indeed had more reason to avenge himself, interceded with tears and cries for you and for all his enemies. If sadness or any adversity, physical or spiritual, distresses you, strengthen your heart and say, “Well, why should I not be willing to bear a little grief, when agonies and fears caused my Lord to sweat blood in the Garden of Gethsemane? He who lies abed while his master struggles in the throes of death is indeed a slothful and disgraceful servant.”
So then, this is how we can draw strength and encouragement from Christ against every vice and failing. That is a proper contemplation of Christ’s passion, and such are its fruits. And he who exercises himself in that way does better than to listen to every story of Christ’s passion or to read all the masses. This is not to say that masses are of no value, but they do not help us in such meditation and exercise.
Those who thus make Christ’s life and name a part of their own lives are true Christians.

Luther, M. (1999, c1969). Vol. 42: Luther’s works, vol. 42 : Devotional Writings I (J. J. Pelikan, H. C. Oswald & H. T. Lehmann, Ed.). Luther’s Works (42:III-14). Philadelphia: Fortress Press.