Contrary to what we usually believe, moments like these, the best moments in our lives, are not the passive, receptive, relaxing times—although such experiences can also be enjoyable, if we have worked hard to attain them. The best moments usually occur when a person’s body or mind is stretched to its limits in a voluntary effort to accomplish something difficult and worthwhile. Optimal experience is thus something that we make happen. For a child, it could be placing with trembling fingers the last blockon a tower she has built, higher than any she has built so far; for a swimmer, it could be trying to beat his own record; for a violinist, mastering an intricate musical passage. For each person there are thousands of opportunities, challenges to expand ourselves.

ISBN 0-06-092192-7
Csikszentmihalyi Mihaly (1996). Optimal Experience: Psychological studies of flow in consciousness Cambridge: Cambridge University Press. "
To achieve a flow state a balance must be struck between the challenge of the task and the skill of the performer.

He is noted for his work in the study of happiness and creativity but is best known as the architect of the notion of flow and for his years of research and writing on the topic. iː/ MEE-hy CHEEK-sent-mə-HY-ee; Hungarian: Csíkszentmihályi Mihály [ˈtʃiːksɛntmihaːji ˈmihaːj]; born September 29 1934 in Fiume Italy – now Rijeka Croatia) is a Hungarian psychology professor who emigrated to the United States at the age of 22. Martin Seligman former president of the American Psychological Association described Csikszentmihalyi as the world's leading researcher on positive psychology.