I have no scripture to back this up. I am just sharing my humble opinion.
The way I see it, I sense the need to fast when I am taking things for granted. Thanking God for all he's given me can become a routine for me. Every once in a while, I'll ask myself, "Hey, what if God decided to hold back?" That's when I fast. Then, at mealtimes I'll remeber I am fasting. Then I'll remeber why I am fasting. Then I am truely thanking God for al he proides for me.
Make any sense?