Schopenhauer noticed a problem with humans: “Mankind was apparently doomed to vacillate between the two extremities of distress and boredom.”
Mihaly Csikszentmihalyi came up with a solution that he calls “flow.” He defines it as, “the state in which people are so involved in an activity that nothing else seems to matter.”
When someone is bored, they must increase the challenges they are facing to get back into flow. When someone is anxious (or distressed, as Schopenhauer put it) they must increase their skills.
But even the state of flow itself is not stable. It is not long before you stop enjoying yourself if you’re doing the same thing at the same level. You become either bored or anxious and then the desire to get back into flow drives you again to either face new challenges or hone your skills.
Source: Mihaly Csikszentmihalyi, Flow, pgs. 4, 75.