How does Junior lose his fear?

Junior had several fears. As a young man, he faced typical school-age fears around acceptance, the ability to succeed, and the ability to talk to girls. He also had more unique fears because of his upbringing on a reservation. He wanted to be able to escape the fate of his family and others he saw as having dead-end, hopeless existences.
To combat his school-age fears, Junior tries to find solace in friendship. On the reservation, he accepts Rowdy, despite Rowdy's tendency towards violent outbursts. At Reardan, Junior plays on the basketball team and befriends Gordy. He also faces his bully, Roger.
His fears about a lifetime on the reservation are addressed in several ways. He escapes his parents' alcoholism through his art. He expresses his feelings and works through his experiences by drawing. When he decides he would like to attend Reardan, he takes his future into his own hands. Leaving the life and people he knows to attend a white, higher-income school is an overwhelming, frightening prospect. Junior considers the transition less frightening than the prospect of staying on the reservation. He faces his fear and makes the decision to attend the new school. When Junior weighs his options, he chooses to face his fears. This is seen in his decision to attend Reardan and in his decision to punch his bully, Roger.
While Junior faces his greatest fears, it is not exactly accurate that he loses his fears. Rather, he accepts the challenges in his life. He uses his art to work through his emotions. He takes action based on the goals he wants to achieve and makes the best of each circumstance.
For more insight, please see the link below featuring author, Sherman Alexie, discussing this book.
https://www.c-span.org/video/?c2439926/user-clip-clip-ithe-absolutely-true-diary-part-time-indiani