My only real fears at the early stage was that family/friend pressure would make continuation unbearable and it did come close to hazardous at a few moments. But even then, I had confidence in what I was doing and negative thoughts in general were not a problem. I was never worried about starvation as I understand the process quite well from my research. The one final concern that came up was the possibility of a healing crisis that would prevent me being able to break the fast on schedule. That would have been a pain.