Mihaly Csikszentmihalyi from the University of Chicago. He wrote the 1990 book called Flow: The Psychology of Optimal Experience.

flow, like creativity, is a state of awareness that covers multiple dimensions. A person is “in the flow” when everything seems to go right, obstacles melt away, and answers come effortlessly. Each aspect occupies its own dimension, yet somehow they get coordinated when flow is experienced. There is a sense of calmness and also the experience of ha