"The cautious child has become a self-willed adult."
Translation:L'enfant prudent est devenu un adulte volontaire.
Someone who is self-willed is determined to do the things that they want to do and will not take advice from other people. He was very independent and self-willed. Il était très indépendant et volontaire. Entêté(e) or têtu(e) is stubborn. I think there's not much difference.