We often use terms such as "existential" and "absurd" to describe works that are both intellectually challenging and depressing, works where nothing seems to happen but something "deep" seems to be going on, even if we can't explain what that is. It's no wonder that Kafka's The Trial has often been associated with these terms because the novel's view of life seems to be pretty dismal. There doesn't seem to be any redemptive moment in the novel where we can say, "Ah, here the main character has shown himself to be heroic or inspiring or exceptionally wise," or "Voila, this is the meaning of life and this is why we should keep on living." Our tried-and-true resources of hard work and common sense don't seem to have any effect in Kafka's world. Instead, in the general spiritual landscape of helplessness, we have characters who confront again and again the hopelessness of their efforts. And corresponding to this general hopelessness is a state of mind that is distracted and exhausted, unable to follow a thought to its reasonable and logical end, unable to formulate a meaningful purpose in life. But this state of mind, at the endpoint of fatigue, is really the heart of Kafka's ironic way of looking at the world, because it is only when the main character grows tired of struggling for his own selfish needs that he gains access to any insight into his life at all.
In The Trial, the deterioration of K.'s capacity to think and reason is a consequence of his subjugation by an irrational and oppressive judicial system.
Against a court system that completely closes off any possibility for resistance, K. still finds a modicum of personal freedom by refusing to completely submit to the system in his final moments. In this sense, he triumphs, because he has revealed a weakness, however small, in a system that is supposed to be omnipotent.