I've done two fasts in my life. Both I had to end on day three. Both times it was because I was getting weak to the point where I was about to faint.
On the last fast, which was two months ago it went like this:
Day 1: very hungry
Day 2: still hungry (even dreaming about food) but not as hungry, and a little weak
Day 3: I woke up and walked to the kitchen... and then I got really weak of a sudden, my vision blacked out and I fell on the floor without even feeling myself fall, and was confused for a few seconds until I managed to get up. This was pretty scary...
Seeing what happened on day 3, I stopped the fast at the end of the day because I had classes to attend to, and couldn't afford passing out while in the subway, or at some bad moment. I was also getting weak to the point that doing really small easy things was arduous.
Anyway I want to try again, and get past day 3 at the very least. Why am I on the brink of passing out like that on day 3? Low blood pressure? Low blood sugar???