Musar על ברכות 9:19

על כל קרבנך תקריב מלח . Rabbi Menachem HaBavli sees this requirement as analogous to the covenant which G–d is reported to have made with the waters of the oceans promising that they would be used for a sacrifice on the altar. Anyone who offers a sacrifice has to cause himself some physical discomfort. Just as salt sweetens the meat, i.e. makes it more palatable, so physical afflictions make his sacrifice of himself more palatable to G–d. Our sages in Berachot 7a expressed this idea when they said: "A single self inflicted pain has more beneficial effect on one's heart than many painful blows administered by outsiders."