Yeah I don't think I could either ... even a 24 hour fast is hard unless you prepare.... get to one meal a day, no snacks, no coffee, reduce carbs to just about nothing and be very well hydrated before you start and during.

I did a 24 hour fast only once,

I have gone longer without eating when I was younger and was sick with something or in a very stressful situation but it wasn't planned it happened on its own and I hardly noticed...

I think the difficultly comes from our minds- knowing there so many hours left until I can eat again. :)