Hm... interesting . I feel that maybe because The Dursleys treated Harry so poorly, he didn't want to inflict that on others and his mother's sacrifice may have strengthened him and brought out the good in him. I am a bit unsure to why he didn't turn out to be a bitter person because as Slughorn said, he was very much like Voldemort, who was in a similar situation. Voldemort had no one, was on his own, felt out of place. Maybe, because he had the love of his mother, the one thing Voldemort did not have-love, Harry could see through the bitterness. I also think that he would have turned out differently, had it not been for the Weasleys and Hermione.