From  How to Believe Again, by Helmut Thielicke, translated by H. George Anderson (Fortress, ©1970)

Excerpt from: How Crises in Faith Arise

...We are all aware of everything that we have to keep in mind, and we also know how the constant round of thinking can wear us down and leave us without a word to say. Do we have any brain cells left over for the process of faith to use? Isn't every thought about God a deviation form the current task we have been given? When bombs are bursting around us, or even when we are in the working-day harness, we have not time fore extra thoughts. And faith, after all, is a thought —or is it?

Certainly everyone has had that experience. And if faith is taken seriously, that experience can make us miserable and sometimes almost tie us in knots. But it is crucial to be clear on this point, because then it become apparent that we cannot base our life on our faith. Faith is often conspicuous by its absence. How few moments there are when I consciously recognize that I am performing an act of faith, when I can establish completely, clearly, and unambiguously, "Now I believe." Furthermore, faith is also very unstable. Sometimes on a quiet evening, perhaps after hearing Bach's St. Matthew's Passion, I am completely filled with faith, in fact, I am downright enraptured. If I should die at that moment, heaven's gates would be wide open. But the very next morning it takes only one blow from an ugly letter to snuff out that feeling again.

No, we cannot base our life on faith. Even the disciples do not live from their faith in that moment when they are battling anxiety and seasickness. They hardly remember that they are believers. There's simply no time to think about it. That may be put very crudely, but that's how it is nevertheless! At that moment the disciples do not live from the fact that God is in their thoughts (because he is not!), but they live because Jesus Christ is thinking of them, and the stillness that surrounds his conversation with the Father is filled with these thoughts about his own. Our faith's grip on the Father may loosen. But he in whom we believe holds us fast in his grasp. Jesus's high-priestly prayer does not stop even when we quit praying. Thus, there is really no such thing as "Psychology of Religion" because the decisive events between God and me do not happen in my psyche, my consciousness, at all; they occur in the heart of my Lord. Here (and only here) there is constancy and faithfulness; here there is a love that will not let me go, even though my fever chart fluctuates between faith and little faith, between trust and doubt, and no reliance can be placed on my defiant and despondent heart. I don't need to tell you what a comfort it can be to know that, and how that knowledge can help me survive those times when my own faith is cold and empty and dead and a sealed heaven arches above me.