These examples suggest what one needs to learn to control attention. In principle any skill or discipline one can master on one’s own will serve: meditation and prayer if one is so inclined; exercise, aerobics, martial arts for those who prefer concentrating on physical skills. Any specialization or expertise that one finds enjoyable and where one can improve one’s knowledge over time. The important thing, however, is the attitude toward these disciplines. If one prays in order to be holy, or exercises to develop strong pectoral muscles, or learns to be knowledgeable, then a great deal of the benefit is lost. The important thing is to enjoy the activity for its own sake, and to know that what matters is not the result, but the control one is acquiring over one’s attention.

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.