The best moments in our lives are not the passive, receptive, relaxing times...the best moments usually occur when a person's body or mind is stretched to it's limited in voluntary effort to accomplish something difficult and worthwhile.
Flow is hard to achieve without effort. Flow is not 'wasting time.
It is when we act freely, for the sake of the action itself rather than for ulterior motives, that we learn to become more than what we were. When we choose a goal and invest ourselves in it to the limits of concentration, whatever we do will be enjoyable. And once we have tasted this joy, we will redouble our efforts to taste it again. This is the way the self grows.
Most enjoyable activities are not natural; they demand an effort that initially one is reluctant to make. But once the interaction starts to provide feedback to the person's skills, it usually begins to be intrinsically rewarding.