In a variation on James's recipe for interesting experience--the familiar leavened by the novel--Hobbs's "art of choosing difficulties" requires selecting projects that are "just manageable." If an activity is too easy, you lose focus and get bored. If it's too hard, you become anxious, overwhelmed, and unable to concentrate. Tellingly, one group is distinguished by its zeal for the kind of work that requires you to give it all you've got: high achievers particularly relish taking on risky projects that have only a 50/50 chance of success.