Fasting is meant to teach humility: If I cannot do without a few sandwiches, I should speak with reserve about being a soldier of Christ.
From “The Awkwardness of Advent”:
Our culture is enduring a severe test of itself. If Christ does not
govern minds and hearts, mere humans will volunteer to do it, and they
will do it badly. When the Judges of Israel could think about their
own existence only with reference to how other people existed apart
from divine regiment, they wanted a human king. Samuel warned them:
“He will take the best of your fields and vineyards and olive orchards
and give them to his servants. . . . He will take the tenth of your
flocks,and you shall be his slaves” (I Sam. 8:14, 17). These days, he
will take a lot more than 10 percent.
And one from Chesterton:
Cobbett said about Cranmer that the very thought that such a being had
walked the earth on two legs was enough to make the reeling brain
doubt the existence of God; but that peace and faith flow back again
into the soul when we remember that he was burned alive.
G.K. Chesterton, William Cobbett (1910).