I wonder if that is a common experience among fasters. There was a tremendous amount of anxiety before being able to just get through that first fast. The concept that helped was Meagan Ramos, one of the founders of The Fasting Method, referring to fasting as "treatment", not to be skipped.
There are other times in this process where anxiety has played a role. For example I wasn't sure I was going to be able to return to fasting if I took a few days off, but I was. There is a ratchet-like characteristic to all of these experiences -- meaning that once you have gotten through the milestone you are then able to rely on that experience.
People refer to the "fasting muscle" in various support groups. It is true that the more that you practice, the easier it becomes. It is also true that you can "strain" this muscle by overdoing it. Meagan Ramos at one point said that approximately 3 36 hour fasts is enough, and that "more isn't more."
Sorting out exercise and fasting took a little patience as well. A lot of us have a tendency to be internally authoritarian with our nutrition and fitness schedules. That turned out to be counterproductive -- it was when I gave myself permission to try different combinations of workout days and fast days that I found a rhythm. Research into "Zone 2" training also helped (read back a few posts in this blog.)
I wanted this post to be a voice of encouragement. There is sort of an "energy of activation" to all of this. As I said, once you get through various key milestones, things do get easier. I recognize though the tremendous anxiety that that first fast causes.
