I always lose some mental quickness and feel cold more readily. Sensitivity to light, sound, smells etc. increases. I get tired during the day and yet thrive on the changes. My mind might complain but my heart and spirit rejoice. The grace and bounties of God come to refresh and renew my being. I do not need to use my mouth.
Instead of craving food, I crave the experience of sacrifice that brings the reward of Spirit.
In a way, during this period I am entering a prison. I realize I am at a disadvantage physically. But also know what I gain, and that imprisonment is temporary. When the fast ends, I have become so accustomed to renunciation during the day that when I see a water fountain, my first response is abstinence. Then I realize I am free, and the enjoyment is heightened. Same with eating. . . it becomes special again.
Meanwhile, I am stronger internally and feel I can conquer mountains.