Robin by Frances Hodgson Burnett

The effect of something like unreality produced in the mind of the mature and experienced by a girl creature, can only be equaled by the intensity of the sense of realness in the girl herself. That centre of the world in which each human being exists is in her case more poignantly a centre than any other. She passes smiling or serious, a thing of untried eyes and fair unmarked smoothness of texture, and onlookers who have lived longer than she know that the unmarked untriedness is a sign that so far "nothing" has happened in her life and in most cases believe that "nothing" is happening. They are quite sure they know -- long after the thing has ceased to be true. The surface of her is so soft and fair, and its lack of any suggestion of abysses or chasms seems to make them incredible things. But the centre of the world contains all things and when one is at the beginning of life and sees them for the first time they assume strange proportions.

It enters a room, it talks lightly or sweetly, it whirls about in an airy dance, this pretty untested thing; and, among those for whom the belief in the reality of strange proportions has modified itself through long experience, only those of the thinking habit realise that at any moment the testing -- the marking with deep scores may begin or has perhaps begun already.