Complex sentence: After being diagnosed with leukemia in 2000 and surviving for five years, Riswold quit advertising to become a full-time contemporary artist, going from "a career of selling people things they don't need to making things that people don't want".
Split into simpler sentences: After being diagnosed with leukemia in 2000 and surviving for five years, Riswold quit advertising to become a full-time contemporary artist. He went from "a career of selling people things they don't need to making things that people don't want".