Elizabeth hates it every time John goes off world. She hates that she has to keep asking him to risk his life, and she hates that he does it even though it hurts her. Even more, she hates that he may not come back. She doesn't want to worry him by telling him how much it hurts her. But he knows.
John knows that his going causes her to lose sleep. But he can't help that he has to. He hopes she understands that he goes so that maybe they will find a way to defeat the wraith. He wants to protect her. She knows.
This time he almost didn't return. She worried for four days before he came through the gate, bruised but altogether all right. She barely got any sleep, and Carson had been keeping a closer eye on her. When she gazes down at him from the balcony above the gate, she hopes that he can't see what this does to her. But he knows.
He holds her close that night as he waits for her tears to dry. He whispers to her how much he loves her as he strokes her hair and runs his hand up and down her back to soothe her. Eventually she calms down and whispers, "I love you," before they fall asleep.
He gives her comfort, not knowing what else to do for her. They both know that he may not return one day. They should accept it.
But knowing and accepting are two different things.