Why are there so few works of Kafka left even though he was a prolific writer?

Context: Franz Kafka was a German-speaking Bohemian novelist and short-story writer based in Prague, who is widely regarded as one of the major figures of 20th-century literature. His work fuses elements of realism and the fantastic. It typically features isolated protagonists facing bizarre or surrealistic predicaments and incomprehensible socio-bureaucratic powers. It has been interpreted as exploring themes of alienation, existential anxiety, guilt, and absurdity. His best known works include the short story "The Metamorphosis" and novels The Trial and The Castle. The term Kafkaesque has entered English to describe absurd situations, like those depicted in his writing.

Kafka was born into a middle-class German-speaking Czech Jewish family in Prague, the capital of the Kingdom of Bohemia, then part of the Austro-Hungarian Empire. He trained as a lawyer, and after completing his legal education was employed full-time by an insurance company, forcing him to relegate writing to his spare time. Over the course of his life, Kafka wrote hundreds of letters to family and close friends, including his father, with whom he had a strained and formal relationship. He became engaged to several women but never married. He died in obscurity in 1924 at the age of 40 from tuberculosis.

Kafka was a prolific writer, spending most of his free time writing, often late in the night. He burned an estimated 90 per cent of his total work due to his persistent struggles with self-doubt. Much of the remaining 10 per cent is lost or otherwise unpublished. Few of Kafka's works were published during his lifetime: the story collections Contemplation and A Country Doctor, and individual stories were published in literary magazines but received little public attention.

In his will, Kafka instructed his close friend and literary executor Max Brod to destroy his unfinished works, including his novels The Trial, The Castle, and Amerika, but Brod ignored these instructions, and had much of his work published. Kafka's work became famous in German-speaking countries after World War II, influencing their literature, and it spread elsewhere in the world in the 1960s. It has since influenced a range of writers, critics, artists, and philosophers.

Answer: Though Kafka was a prolific writer he struggled with low self-esteem and destroyed 90% of his work. Rest of his works were lost or were not published. In his will Kafka instructed that his unfinished novels be destroyed, luckily those instructions were ignored and we are able to read his novels like The Trial and The Castle.