Yeah, human body is so resilient. I've done the 72 hour fast three times and I now fast one day a week for 24 hours, from Wednesday breakfast to Thursday breakfast. I expect that I'll fast for 72 hours once or twice a year from now on as well. I see it as spring cleaning for the human body.
I found a surprising revelation of fasting was how habituated I am to eating at regular intervals. After fasting past 24 hours, when my glucose reserves were used up, and my body entered ketosis, my actual feelings of hunger leveled off. I could easily forget the hunger by staying engaged in some other activity.
That is, until my regular meal times. During regular meal times, I found I'd have an increase in the desire to eat that was definitely not related to my feelings of hunger. For example, I'd walk through my kitchen and find myself reaching to open the fridge, or planning out a meal, as it was meal time. I'd catch myself, and remembering I was fasting, and move on. It was so weird, but it was cool as this experience has made me aware of how my eating habits are actual habits that affect me on a not quite conscious level. Now that I am more conscious of these habitual feelings, I have an easier time making healthier eating habits.