One of the points of fasting is that we would show no mercy to our own sins. Our bodies are temples of the Holy Spirit and thus we are God's people, the new Israel.
If we dare to engage in a spiritual reading of the Scriptures, we find a valuable lesson in Deuteronomy 7.
“When the Lord your God brings you into the land that you are entering to take possession of it, and clears away many nations before you, the Hittites, the Girgashites, the Amorites, the Canaanites, the Perizzites, the Hivites, and the Jebusites, seven nations more numerous and mightier than you, and when the Lord your God gives them over to you, and you defeat them, then you must devote them to complete destruction. You shall make no covenant with them and show no mercy to them. You shall not intermarry with them, giving your daughters to their sons or taking their daughters for your sons, for they would turn away your sons from following me, to serve other gods. Then the anger of the Lord would be kindled against you, and he would destroy you quickly. But thus shall you deal with them: you shall break down their altars and dash in pieces their pillars and chop down their Asherim and burn their carved images with fire."
Just as Israel was not to show mercy to the forces within her borders who would corrupt her, so we are to show no mercy to the forces within that corrupt us, namely our passions and vices.
The truth is that we sacrifice to what we worship. And the Lord knows there's a lot of things that we sacrifice to other than Him. Just like Sodom and Babylon, every culture has its own niche of idolatry that they are known for. Modern societies, and the United States, are no different. We are bombarded in our culture by its running norms and principles, and having whatever you want to eat whenever you want to eat it is extremely high on our society's particular list.
So, today was a difficult day of fasting. Work was long and I'm really tired. I'd love to just eat whatever, rather than think about doing this and spiritual things. But I made it. I'm off to bed before another work day tomorrow.