With their still-developing brains, adolescents can shrink from behaving in ways that serve their long-term interests. It’s easier to punt on geometry homework when Instagram beckons, and delay turning out the light when friends are sending midnight texts. Soiled clothing in a pile on the floor? Not a priority. Like everyone else, even teenagers with the best intentions can fall into habits that undermine their goals and are bewildered about how to construct the habits that will improve their lives.