For choreographers, the postpartum pangs that follow a big triumph can summon doubts about their ability to duplicate a career’s artistic zenith. Critics sneer, ballet masters and directors stifle skeptical looks, audiences question, producers pressure and choreographers agonize about the label of “one-hit wonder.” Has he backed himself into a corner? Has she burned out on ideas? How do you bring something original to the stage without copying yourself or experimenting with disaster?