you can do anything you want to do, if you want to do it.
but your body is your mind and if your body doesn't want to do something then neither will you. so some people can't do things, it simply isn't their fault that they don't want to do them, they can't! so how do you tell the difference between someone who has the ability to do something but chooses not to and someone who does not have the ability, and can't. in both cases, their bodies don't want to do something, so all we can say is that they don't want to do it, whether they can or cannot.