The thing with stating facts that delimit someone's upper potential in anything is that it's just human nature to attribute any sort of struggle we encounter along that path to be due to those restrictions even if it's really unrelated to that specific problem - can't win in a competitive video game? Must be because I'm getting older and I don't have the reaction time any more... Struggling with schoolwork? I guess I'm just not smart enough.. etc etc. Strictly speaking there are ceilings but their exact relationship and the concrete limits they place on an individual's ability is an extremely tricky thing to say with any definitiveness. So it's best to constantly assume that roadblocks are due to a failure of current methodology rather than some intrinsic limit. There are certainly some absolute limits in sports, like the objective advantage of shorter statures in gymnastics, but excepting cases on the extreme opposite ends of the spectrum it's still very tenuous to make any definitive statement. Hence, err on the side of "doable"