in Thoreau’s Journal:

I am struck by the fact that the more slowly trees grow at first, the sounder they are at the core, and I think the same is true of human beings. We do not wish to see children precocious, making great strides in their early years like sprouts, producing a soft and perishable timber, but better if they expand slowly at first, as if contending with difficulties, and so are solidified and perfected.