Rumble is a great flyer, and more diligent in his training than anypony else; but he's still not at the level he should be, if he plans to make it as a future Wonderbolt. Why are some ponies—like Rainbow Dash, like his brother Thunderlane, like his best friend Eddy—born with all the talent in the world, while ponies like him have to suffer just to attain mediocrity?