I've pushed fasting/detox too far in the past, when my body was very toxic, and I regret it, it actually did more harm then good. You really need to adapt to your specific situation/needs.
Sometimes the body needs fibers, greens to get rid of all the toxins. Or, you need extra energy to be able to move/be active to flush out the system. Or, you need total rest and relaxation.
It's very dangerous to play with detox the wrong way, I've done my mistakes in the past... Getting older=getting wiser/more experienced (for me anyway lol)