And this shall be to you a law for all time: In the seventh month, on the tenth day of the month, you shall afflict your souls [teannu et nafshoteichem]; and you shall do no manner of work, neither the citizen nor the alien who resides among you. For on this day atonement shall be made for you to cleanse you of all your sins; you shall be clean before Adonai. It shall be a sabbath of complete rest for you, and you afflict your soul [ve-innitem et nafshoteichem]; it is a law for all time. (Leviticus 16:29–31)
Yom Kippur isn’t an easy day. Not because of we are fasting. I agree, fasting is one of the duties of today, as commanded in the Torah, but fasting in itself only needs a bit of physical strength. If, God forbid, we are ill, or get sick, we are even commanded to break our fast.