Nijinsky was a special case. He choreographed Stravinsky's Rite of Spring, a pagan ritual of human sacrifice. The dancers wore ugly costumes, had their toes turned in, made spastic movements. He left the composer's dual tonalities and rhythms alone and just made movements to the simple melodies. It was a work of genius 50 years ahead of its time, performed in front of a Paris audience dressed in evening gowns and opera combs. A riot ensued. I think he became mentally ill partly because he was gay and married anyway, and partly because the world broke his heart.