Self-esteem is the most important aspect of mental health. Without self-esteem, how can you expect to live your life free of anxiety, depression, or general angst? I don’t see where positive thinking comes from unless you are happy about yourself. I don’t understand how you can want to live if you don’t want to be yourself while living. Even if some mental problems are proven to have biological origins, self-esteem is required to (a) want to do something about them, and (b) to reduce their intensity. You can’t lose by gaining self-esteem. Self-esteem isn’t something you happen upon, or someone gives you, or something that “comes to” you by divine inspiration or revelation, all at once. It’s the product of thinking rationally about yourself, about others and about life. A therapist cannot “give” you self-esteem. A therapist can help you learn and internalize rational ideas and viewpoints that foster self-esteem, if you’re willing to consistently start acting upon those viewpoints.