Let us use fasting to make up for what we have lost by despising others. Let us offer our souls in sacrifice by means of fasting. There is nothing more pleasing that we can offer to God, as the psalmist said in prophecy: A sacrifice to God is a broken spirit; God does not despise a bruised and humbled heart.
The whole thing is here. Now that I read it, it makes perfect sense. It also reminds me of something St. Patrick wrote in his Confessions, how when he was a slave tending sheep in Ireland he was often cold and hungry, and that made him humble. I've always lived in physical comfort, but I think I can see how suffering from hunger would help you remember that you're not as awesome as you think you are.