The Decisive Years
From Reiner Stach, Kafka: The Decisive Years (translated by Shelley Frisch):
Asceticism was a magic word for Kafka, an intricate complex of images, cultural paradigms, idiosyncrasies, fears, and psychological techniques that he incorporated into his thought that feelings and gradually made a focal point of his identity. He was entirely justified in asserting that he had ‘a fabulous innate capacity for asceticism’. It is remarkable how tenaciously he clung to the rule of self-abjuration once his period of dawdling came to an end. The way he steadfastly denied himself warmth, meat, drugs, and medicine clearly refutes his alleged weakness of will. He reduced his good intake, toughened his body, and simplified his habits. […]
Asceticism is not austerity for its own sake; it is a process of self-regulation and self-formation based on the utopian notion of attaining complete control over one’s body, self, and life. All Kafka’s interests, habits, and penchants were modified accordingly. A diet of nuts and fruits, a flawless method of chewing, devotion to calisthenics, and long walks. He cultivated and shaped his body. He gained awareness of his body as well. He felt a growing aversion to and even loathing for everything that threatened to undermine his new sense of autonomy, especially doctors who treated his body as though they were plumbers, and medicines that had unanticipated side effects. He contended that it was degrading to battle insomnia with valerian: his insomnia was not caused by a lack of valerian.