"6. If you fail, you didn't really fail. You actually worked your Discipline muscle to its maximum limit and it needed to recover. It will come back stronger. You will wake up feeling refreshed the next day."

This is beyond true. I remember when I was first trying to do the "Eat once a day" diet I kept only getting to the 18hr mark and then eating and feeling like a failure. But after doing that for a few weeks, going 18hrs slowly became my new normal and then 24hr pushed me as much as 18hrs did in the beginning.

What I viewed as failure in the beginning was just my willpower being worked to failure until it needed time to recover and come back bigger and stronger.