I'm on day 17 of my fast. I am not fasting for serious health problems and have been in relatively good health. My personal experience is that the fast gets more difficult on days that I've laid low and rested. I've gone to my job on weekdays and have found that pretty easy, but it's a desk job. After work I take a nap for about 90 minutes, then I tackle a bit of housework. I find my stamina when doing even a slightly strenuous task is depleted quickly and I've had to cease doing some longer tasks mid-stream to rest, then tackled it to finish it the next day. I seem to do better when I am active on weekends. As people before me have said, listen to your own body. One thing we all experience is that you will not be able to avoid listening! Your awareness of everything is heightened during a water fast!