Actually, I disagree with you. I think fasting is like a muscle, like many people and doctors have said. At any rate I did exactly what you suggested. I tried fasting for a while, I couldn't. Gave it two months (waited for the summer when I would be more free), tried again and keep on failing. I did a calendar of my past month, and I realize that my failures always due to my inability to be in complete rest. I always fail around day four, which is the day that I feel the weakest. That is why I decided to stop until I can actually go to a retreat and be complete cut-off from the outside world, and more importantly I do not have any obligations. Maybe in one year I will have saved up the money, and I will be able to make the time to do that.