My 2pworth: you're on the right track emphasising making mistakes and keeping going (though I'm not sure I'd define smart as that - he's going to discover that other people have a different definition, sooner rather than later). The trick is going to be making sure he gets enough of a chance to be smart in your sense. I think humility (in a good sense, which I guess is what you mean!) comes from knowing you have to work, too, and can fail, too. So I vote: do everything you can to make sure he gets things to do that are hard for him. Maybe it's wishful thinking, but I think it won't much matter what other people say to him about his abilities - if you're matter of fact about them, focusing on what he needs to work at, just as you would with any other child, I think he'll be matter of fact about them.
