Not everything that is difficult is thereby good training. It’s easier to withstand getting punched in the gut if you’re in good physical shape, but I wouldn’t suggest trying to get in shape by having someone punch you repeatedly in the gut.
(Indeed, at some point of martial arts training it’s useful to learn how to take a punch, but this training has to be done carefully and sparingly. You don’t become stronger by rupturing your spleen.)
Not everything that is difficult is thereby good training. It’s easier to withstand getting punched in the gut if you’re in good physical shape, but I wouldn’t suggest trying to get in shape by having someone punch you repeatedly in the gut.
(Indeed, at some point of martial arts training it’s useful to learn how to take a punch, but this training has to be done carefully and sparingly. You don’t become stronger by rupturing your spleen.)