Nighttime was everything he feared.  It was when there was no sun, no advantages for him, all advantage over him.  It was when he was helpless against any other bender.  It stood for the temporary domination of the moon over his power, his rays of light.  It was his weakness.  It was the Fire Nation's weakness, not that he considered himself a part of the dishonorable nation anymore.  Nighttime was everything he hated, everything he was afraid of.
    Nighttime was when he used to feel dead.
    But then she came.  She loved the night, the moon.  She was the night, she was practically a living embodiment of the moon.  She was the one who had the advantage over him when they fought under the stars.  It was she who drew power from his weakness.  She hated him and everything he stood for.  He had thought he had hated her and everything she had stood for.
    But the feelings he had as he fought with her under the watchful eye of her moon, her rays of light were not that of hate.  He did not feel weak (well, not mostly), he did not feel afraid.
    He did not feel dead.
    (In fact, he had felt more alive than he had felt ever before, encased in that black box of nighttime with this embodiment of his lovely moon.)