I just finished 5 days, and it was SUPER hard!
I can tell you that I tried in the past, but I think I was too toxic to make it through a day. Eating mainly raw vegan for the past year I think helped a lot.
I'm def not an expert, but what really helped me was keeping in mind all the reasons why I was doing it; if you are really struggling with some health issues that won't go away, there is kind of nowhere else to turn! You gotta just push through!
It seems easy for some people, but I can assure you it was anything but easy for my. Second day I thought I might have a heart attack due to increased heart rate, I had zero energy, and I kept a barf bucket beside me in bed, though I never puked. I was sooooo hungry the entire 5 days. I'm active and thin and people would think I am healthy, but I know I have years of childhood toxins preventing me from true health. Think about your end goal, and maybe it will be easier! Good luck!!