My intention yesterday was to fast for 36 hours, but I broke the fast at 24 hours. I had a meeting a couple of hours away today, and didn't want to risk having the runs (a side effect that I hear is common in fasting) on the expressway.
Someone I respect said that if you are going to break a fast, and have made it to 24 hours, then that's a real accomplishment -- not to worry.
I don't think this is going to completely derail my program, but we will see over the next few days. I'm fasting now and it feels approximately like it did before I "fell off the wagon".
--edit: I'm right back on it!