Denying or suppressing parts of ourselves is, I believe, what often contributes to anxiety/depression, addiction, self-esteem problems, shame, and many other issues. 

Psychotherapy is a process of coming to understand these reactions not as defects in ourselves, but as creative adjustments that we made at times when, perhaps, we had limited inner resources available to us. Psychotherapy leads to an increase in self awareness. One becomes more aware of the significance of their relationship with the therapist as it develops over time, and can then use this awareness to help them make changes.