Similar to the word tenacious with specificity towards young adults aged 13-19. The act of being so stubborn in one's teenage mind that (s)he will triumph over adversity through sheer force of will.
I told him he'd never make the Varsity tennis team. He was so teenacious that he practiced every day for 3 straight months and made it.
Reverse psychology doesn't work on her. She teenaciously holds on to her beliefs.