It's true that you don't know what you've got until it's gone. You don't miss the air until you can't breathe, and he knows better than anyone because sometimes, he still struggles to draw in that next breath.
He misses her. All he can do is hurl himself into battle, and throw the grief away. Now isn't the time for grief. They have to finish what she started.
But even if he does, she won't come back from those crystal waters.
He can't get her back. But the memory of her smile is as precious to him as liquid gold.