defiant wistfulness of his own" expresses a very complex mix of emotions and behaviour patterns.
Explanation:
While wanting to be liked, the person was at the same time harshly sad and melancholy, and maybe sometimes expressed his emotions in an aggressive way. It is not something that can be understood completely without reading more about the character in question.
he heart of 'wistfulness' is a longing, usually in the eyes; a person is wistful when they desire something intensely, usually something they know they can't have.
