She is tired all the time, but not the kind of tired that goes hand in hand with exhaustion. She is tired when she lays her head down at night, and tired when she lifts it in the morning. A weariness has settled in her bones, and it makes simply moving through the day difficult. And she feels like there is something broken inside, something that aches and twists and churns, and that leaves her feeling profoundly empty. Like there is a hollow space in her chest that makes her feel both numb and unfulfilled.
She wonders why that emptiness grows all the more fathomless when she meets his gaze, wonders why her exhaustion is all the more palpable when he is not by her side. She wonders why Aang's love is not enough to fill the hole in her heart, why his kisses no longer make her stomach flutter. She wonders why, in the dead of the night, she has the sudden, irrational urge to be wrapped in strong, warm arms- arms more larger and more muscular than Aang's could ever hope to be; wonders why warmth curls in the pit of her belly when Zuko makes her laugh.
And then, one day, out of nowhere, the answer hits her. She is in love with him, honest to the spirits, in over her head, truly and deeply in love with him. The emptiness, the weariness, are not merely from the last vestiges of the war. They are from the knowledge that what she wants most is the one thing that she can never have. How could she ever look into Aang's gray, gray eyes and tell him that she does not love him? That she has fallen in love with his teacher and friend instead? How could she bear to hurt Mai, the stone faced, quiet young woman who hid a tender heart behind a stony wall of grief? And how, how could she face Zuko, one of her closest friends, and face rejection at his hands? She can not. She does not have the strength.
Or possibly, she is too strong. She is strong enough to shoulder the pain, to make peace with the emptiness; to live with the weariness so that she will not hurt those whom she loves. So she buries the pain and pretends to smile. She hides her heart and continues being her friend's lover and her lover's friend.