The chapter gives an overview of research on metacognition in writing and distinguishes between learners' metacognitive knowledge about writing and metacognitive regulation of writing. The empirical study investigates one language learner's reflections about his own writing processes during the course of a writing intervention in German as a third language. Keystroke logging software and screen-recording software were applied during the writing processes and then used as a tool by the author for recall interviews following each writing session. The study shows that when given the chance to reflect on their own writing, detailed accounts of metacognition on writing in a foreign language can be produced by students. The interviews revealed that the student had a strong focus on his linguistic limitations in the third language and that he associated writing mainly with feelings of insecurity, frustration and dissatisfaction. The author argues that foreign language lessons should provide time for reflecting about learning and discuss learners' potential negative self-images, which might lead to their avoiding challenging tasks and hinder further learning, should be discussed.