Harry, the way I see it, could withdraw from every living person or find employment as a collections worker and it still wouldn't change the essence of who he is. He started this whole train ride trying to save Hermione and has a feeling that Draco needs to be saved, as well. I'm not sure if he's fully aware that the train ride is about to become a train wreck but I just don't think he's capable of not reaching out and feeling it is his responsibility to help those he loves. I don't want to use the word "hero" with Harry because I feel is diminishes who he really is. Maybe "savior" did, too. Harry is a beautifully flawed light that seeks to banish darkness when it creeps around those he loves. Yep. That's what I meant to say the first time....