In Inside Out and Back Again, Ha's life comes back when she learns the true meaning of how to live a life that is "not the same, but not bad at all."
The premise of the question rightly presumes that a part of Ha's life ended when she left Saigon. The world in Saigon represented so much of her identity. From the papaya tree to her mother's stories to her academic achievement, Ha's sense of identity was tied to her life in Saigon. In having to leave because of war, Ha loses a significant part of her life.
Ha must learn to establish herself in the midst of adversity. As a result of perseverance, Ha's life returns. For example, she realizes that in Alabama, her lack of language skills puts her at a disadvantage. When she was in Saigon, Ha loved to talk. With her move to Alabama, she lost some of that and, with it, part of her life disappeared because she was relegated to silence. However, in her tutoring sessions with Mrs. Washington, Ha gains greater confidence with her English. Ha's growing comfort with the language is evidence of how her life, or identity, is returning. She shouts back against her tormentor, Pink Boy. She communicates and makes friends with Steven and Pam. Ha knows that life is different for her in Alabama. Yet, Ha is able to make a life for herself in America. She no longer accepts what she used to believe that life in war time Saigon is better than peace in America. In establishing herself in America, Ha gains her life back because she embraces the internal toughness needed to triumph over adversity.
An essential component to reclaiming Ha's life lies in absorbing two lessons from her mother. The first is what she realizes after her mother prepares the Americanized version of papaya. Ha tastes the food and realizes that it's "not the same" as what she knew in Saigon, but it's also "not bad at all." Ha realizes that her mother's lesson is a way for her to get her life back. She might not be the girl in Saigon. However, she can be a wiser and more mature one in Alabama. The second lesson she learns from her mother that helps her get her life back again is in how the Tet New Year means that "luck starts over." Ha recognizes that she does not have to live a life full of past regrets. She can get her life back because she can live for today and tomorrow. It is for this reason that Ha closes the narrative with her beliefs on the "fly kick:" “This year I hope I truly learn to fly-kick not to kick anyone so much as to fly.” She previously wanted to learn the martial arts move to defend herself. Now, she appropriates the language of the move to show growth and maturation. This is evidence of how Ha's life is coming back again.