Experiences with extended fasting

Recently I've been reading about the benefits of doing an extended water fast. There are apparently benefits when it comes to entering autophagy for cell repair, as well as increases in stem cell production in the a couple of parts of the body. I believe there is also some data to suggest that it increases sensitivity to insulin and does some lasting things to ghrelin and leptin levels. Many people also report clearer thinking, feelings of euphoria, and increased levels of focus after the first day of fasting.

After reading these benefits I decided to try a 72 hour water fast. Unfortunately, I did not feel almost any of the acute effects that were described in most all places that fasting is discussed. For both of the nights that I was fasted I woke up slowly and felt lethargic for a couple hours after waking. I had fairly severe brain fog throughout most of the second and third days. I was drinking electrolyte water, as is suggested (trying to hit 3g sudium/potassium and taking 250mg magnesium supplement/day), but when I drank that at a rate where I would be able to get all of the electrolytes in throughout the day I would have GI distress. I was only able to stomach about 1-2g of sodium/potassium per day

There were times where I felt the focus/energy that was described by other posters online, but it always came with an asterisk. I felt as though I was slightly detached from myself? Almost as through I was sitting inside my own mind/body and driving it as a third party. I will say that after the 18 hour mark I only felt hungry a couple of times. I did have a lot of thoughts about food, but those came from being very introspective about the fact that I was fasting more than anything else.

I want to believe that I did something wrong and thats the reason that I was not able to get the experience that it seems most others do; I would be willing to give it a second shot, but I want to try and figure out what could be improved.

Has anyone else here tried a 3+ day extended fast? What were your experiences?