Well, I haven't intentionally tried to do fasting beyond the 18-20 hour mark during chronic IF. The afternoons could be tough on the second day for me. Actually it forced me to find a nice meditation spot where I could spend my lunch calming down and attending to my focus. I was probably a much better co-worker on sunny days. Oh, I should mention that it would have been really easy to just work through lunch given I had higher energy and focus levels. Eventually though, a walk or something active mid-day became essential if I didn't want to end my days in robo-mode.

Evenings were always easier for me on the tail end of the IF routine; I sometimes enjoy cooking; I had an excuse to plenty of whatever sounded good, and when you have a four hour window to eat, food tastes so much better its shocking.