Musar for Taanit 44:11

But the bad sort of Separation is that of the foolish gentiles who abstain not only from taking of the world the non-essential but also from taking that which is essential. They smite their bodies with sufferings and strange afflictions which G-d does not desire at all. On the contrary, our sages said: "it is forbidden for a man to afflict himself" (Taanit 22b). And regarding charity they said: "whoever needs to take but does not take is as one who sheds blood" (Yerushalmi end of Peah). And likewise they interpreted: "'a living soul' - the soul that I gave you, keep it alive" (Taanit 22b). And "whoever sits in fast is called a sinner" (Taanit 11b), which they qualified as being in the case where a person is unable to withstand it.