Intrapersonal communication is the communication process that happens internally. Communication with others is dependent on individual perceptions, and those perceptions are developed with the communication that happens within the individual.
Benjamin Lee Whorf was a linguist in the 1930s and believed that the content of human thoughts impacted human behavior. For example, an individual having a bad day will only make it worse with negative self-talk, while an individual having a great day can make it even better with positive self-talk. However, Whorf's larger view was that the thought processes of an individual are shaped by the grammatical structure of the language.