David Copperfield is a story of the narrator's youth, as he's struggling to find a place to belong in an often changing, not always welcoming English middle-class society. Still, even though this is a novel all about David's development away from youth, it's also about his nostalgia and disappointment that success has to come at the price of innocence. All of the things that David learns about human nature during the novel – with Mr. Murdstone and Mr. Creakle's abuse, with Steerforth's betrayal, with Uriah Heep's manipulations – give him the added maturity he needs to sympathize with others and succeed in the world. Still, these painful experiences have come at a cost. David remembers the purity of his heart when he was a little boy with Mrs. Copperfield and when he was courting child-like Dora with a pang of sorrow for the good person he used to be.
The narrator's tone of pity and nostalgia towards his own younger self increases our identification with David as a character.
As much as Dickens celebrates the virtues of the young, he criticizes spoiled adult women characters such as Dora Spenlow, who rely on others to protect them as though they were children.