Throughout the ages there are stories, stories of gods and angels, monsters and devils, heroes and villains, and in all of these one thing is certain.
"Pride goweth before the fall".
But what of a hero stripped of pride from the beginning? One touched by fate and blessed with power, but freed from the hubris that felled so many before? There are many titans of magic and power, and all them are remembered in either glory or infamy. But what of a humble demigod? A wielder of supernatural power unfettered by pride.
Surely such a being could not abide in magical Britain, the land of heraldry and the glory of bloodlines of past deeds, but it is there that he was born. There that he fought. There that he died. Or did he? Some say that he stole away in the night after his victory over evil, fled away across the sea to one who knew his heart and not just his name, and bade all he met to forget his passing, to forget he was ever there. But, this is nonsense of course. After, there is no such thing as a demigod stripped of his pride.
Basically, Harry is not just another person, but someone well and truly blessed in power. Like a hero from myths, the guy has it all. Power, persuasiveness, luck. The one he doesn't have is ego. He was told his whole life he was worthless, and eventually he started to believe it. As he grows and matures however, people begin to realize he is no ordinary person. Like some mythic king of old he simply grows and grows until he looms over all he sees and his only equals are others that loom as large.
The world he was born into was dying, choked by one and barely held onto by another, and so the stage is set for Harry to set out on a crusade, and to fade away when it's done. His one escape being the only person who has the perspective of distance from the situation.