Every day, people are emotionally hurt, but they manage to make it through those hard times. With these hard times comes knowledge and wisdom, such as how to avoid those things that hurt you.
Like the theme, Tina is able to overcome those difficulties and be a stronger person because of it. She is stronger because she knows that not everyone is going to be nice and it is up to her to be the difference.
It teaches us how to be different from those harmful things or people. It also teaches us how to make the world a safer place for everyone through kindness.