Primarily, by pretending that a "usually" is an "always". "Real success is never accidental" is, empirically, definitely false. "Real success is almost never accidental" would be the less strong, but more correct, version.

That would depend on what you mean by success now wouldn't it? If you believe people who take calculated risks and get unlucky aren't successful, then perhaps you're right. But you can't claim you can make a statement more correct by assuming you know what every word means. Parsing ambiguity is part of rationality. (Though my downvotes would indicate it's not...)