I have never really fasted with a spiritual, religious motivation. And even though, I grew up in church and saw my mother doing it and knew that Jesus did it, or that there was some Biblical benefit, I can't recall that the times I've done it has been with that in mind. I fasted recently not with that in mind and I don't think it went great only because I knew that my motivation was not driven by The Bible.
I get what everyone has shared about self control and so on, I just don't get how it benefits the spirit? Maybe when I do it i'll understand. I appreciate all the responses though.