Katrina's casual words make Aaron angry. "Stop it!"
Although he knows that she's only doing it to feign optimism, Aaron feels a surge of pain in his heart at her casual take on her life. It's more painful for him to see than the previous dejected expression on her face.
To stop her from spouting nonsense, Aaron gathers her in his arms. He holds her tightly, pressing her body against his.
How could she talk about her own life like this? He can't let her think this way.
As long as Aaron is alive, he won't let her leave him. Even if she flees to the other end of the world, he will follow her and get her back. Even if she tries to kill herself, he will bring her back from the dead. He won't let her go anywhere unless it's by his side.
Katrina is his woman.