It hurts the most not when they don't fit in this world, but when they do. Pain, after all, doesn't strike when you're whole, but when you lose something.
Lucy is certain that she could easily stand the jeers and strange glances, the worried look in her mother's eye when they slip up and say the Lion where they would have once said Christ, if that was all she had to bear. She thinks that no matter how unpleasant it is to have her tentatively burgeoning fashion sense mocked for being old-fashioned, the sneers would be infinitely preferable to following the latest trend. But she has no choice in the matter. She's a child now, and children take the shape of their surroundings.
Still, she consciously tries to remain a Narnian. Some things are easy: she continues to swear by the Lion, despite her mother's reprimands. Others…are not so easy.
For the longest time, whenever she saw or heard of someone badly wounded, her hand would gravitate automatically to her hip, her fingers searching for the soothingly cool glass of her vial. And no matter how awkward that could be – 'Lucy, darling, are you all right?' – she would smile privately to herself after it happened. Because that instinctive, insignificant action proved, didn't it, that she was still a Narnian?
Eventually, though, her fingers stop twitching for her vial at the sight of blood, and although she sometimes moves her hand deliberately, pretending to be searching for it, it's a sham now, a forced action. She's lost a little bit of what made her a Narnian at the core, and this is what makes her weep at night.
What hurts the most, as she tries to tell Peter, is not being so starkly different, but being so incongruously the same. It kills her that they are able, in so many ways, to slip back into their old, old life, as if they had never left it, as if Narnia really was just a child's pretend game.
They have so quickly adopted the right style of speech, as Susan calls it sometimes, and Lucy feels like crying every time her siblings address her, not in the fluent, flowing style of Narnians, but in the humdrum, every-day language of ordinary schoolchildren – the language of schoolchildren who've never been granted the privilege of loving Narnia. They begin deferring automatically to their mother, after a month of forgetting to tell her whenever they leave the house and arriving home past curfew. Soon it is second nature – they don't need to write the time they're supposed to be home on their hands in ugly black ink. They remember and obey it automatically, because it's just part and parcel of being a child –
But they're not children, or at least they weren't.
She hates that they have bowed and bent to conform to this world, spent so much time in the moulds of ordinary children that they have lost what she's convinced is their true shape. Aslan would be disappointed, she thinks, or maybe he wouldn't be, maybe he'd understand.
Because what's fifteen years in Narnia compared to the rest of their life?