J.K. Rowling impresses me as an author, but she may be underperforming. It would be interesting to sit down and chat with her concerning motivation and literary intent. She sets up some great paintings of grace and then leaves them all unfinished! The "good guys" are all seemingly divided between the really good people (like Albus Dumbledore) and the small-minded, often bitter people (like Dolores Umbridge). There are MANY opportunities for people in the first camp (like Harry) to reconcile or forgive people in the second (like Draco Malfoy), especially since they often share similar hurts and a common enemy; it certainly would prevent lots of forthcoming pain.
Somehow, HP #5 came across as preaching the value of self-control more than grace. But I guess grace is hard to come by in wartime. (The word "supernatural" comes to mind.) And most authors suffer from the misunderstanding that it simplifies the dramatic picture. They confuse grace with resolution, I reckon.