structural:expansion, quality:corruption
Personality

Kafka had a lifelong suspicion that people found him mentally and physically repulsive. However, many of those who met him found him to possess obvious intelligence and a sense of humour; they also found him handsome, although of austere appearance. Kafka was thought to be "very self-analytic". Brod compared Kafka to Heinrich von Kleist, noting that both writers had the ability to describe a situation realistically with precise details. Brod thought Kafka was one of the most entertaining people he had met; Kafka enjoyed sharing his humour with his friends but also helped them in difficult situations with good advice. According to Brod, he was a passionate reciter, able to phrase his speech as though it were music. Brod felt that two of Kafka's most distinguishing traits were "absolute truthfulness" (absolute Wahrhaftigkeit) and "precise conscientiousness" (präzise Gewissenhaftigkeit). He explored inconspicuous details in depth and with such precision and love that unforeseen things surfaced that seemed strange but absolutely true (nichts als wahr).

Kafka's letters and unexpurgated diaries reveal repressed homoerotic desires, including an infatuation with novelist Franz Werfel and fascination with the work of Hans Blüher on male bonding. Saul Friedländer argues that this mental struggle may have informed the themes of alienation and psychological brutality in his writing.

Although Kafka showed little interest in exercise as a child, he later developed a passion for games and physical activity and was an accomplished rider, swimmer, and rower. On weekends, he and his friends embarked on long hikes, often planned by Kafka himself. His other interests included alternative medicine, modern education systems such as Montessori, and technological novelties such as airplanes and film. Writing was vitally important to Kafka; he considered it a "form of prayer". He was highly sensitive to noise and preferred absolute quiet when writing.

Pérez-Álvarez has claimed that Kafka had symptomatology consistent with schizoid personality disorder. His style, it is claimed, not only in Die Verwandlung (The Metamorphosis) but in other writings, appears to show low- to medium-level schizoid traits, which Pérez-Álvarez claims to have influenced much of his work. His anguish can be seen in this diary entry from 21 June 1913:

and in Zürau Aphorism number 50:

Alessia Coralli and Antonio Perciaccante of San Giovanni di Dio Hospital have posited that Kafka may have had borderline personality disorder with co-occurring psychophysiological insomnia. Joan Lachkar interpreted Die Verwandlung as "a vivid depiction of the borderline personality" and described the story as "model for Kafka's own abandonment fears, anxiety, depression, and parasitic dependency needs. Kafka illuminated the borderline's general confusion of normal and healthy desires, wishes, and needs with something ugly and disdainful".

Though Kafka never married, he held marriage and children in high esteem. He had several girlfriends and lovers during his life. He may have suffered from an eating disorder. Doctor Manfred M. Fichter of the Psychiatric Clinic, University of Munich, presented "evidence for the hypothesis that the writer Franz Kafka had suffered from an atypical anorexia nervosa ", and that Kafka was not just lonely and depressed but also "occasionally suicidal". In his 1995 book Franz Kafka, the Jewish Patient, Sander Gilman investigated "why a Jew might have been considered ' hypochondriacal ' or 'homosexual' and how Kafka incorporates aspects of these ways of understanding the Jewish male into his own self-image and writing". Kafka considered suicide at least once, in late 1912.