According to Strength, Pleasure, and Happiness

In 1912, Kafka wrote "The Metamophosis", "The Judgement" (which he wrote in one night), large segments of Der Verschollene (Amerika), and published his first book, Meditation. It was the same year he met his fiancé, Felice Bauer. He described his daily routine to her in a letter:

From 8 till 2 or 2:20 office, until 3 or 3:30 lunch, from then on sleeping in bed (usually just trying to, for a week in that sleep I saw nothing but Montenegrins with an extremely disagreeable, headache-inducing clarity of each detail of their complicated costume) until 7:30, then 10 minutes exercise, naked at the open window, then an hour walking alone or with Max [Brod] or with some other friend, then dinner with my family, then at 10:30 (although it’s often as late as 11:30), sit down to write and stay at it according to strength, pleasure, and happiness until 1, 2, 3 in the morning.

- from Kafka’s Prage: A Travel Reader by Klaus Wagenbach