Diminishing Marginal Utility

So I was nice for a day. That day is gone and I am back to being my old self. In my economics class today, I was teaching the concept of diminishing marginal utility..a little tough for high schoolers, but nonetheless important. Our demand for something will shrink at a faster rate as we use more of the product or item. Unfortunately, this basic economic concept applies to learning and knowledge it seems. Now I view each day a gift and have set an important goal..to learn something new each and every day. My quest and thirst for learning grows each day. I remain inquisitive and interested and wish for more and more as I learn. So I am bucking the trend of diminishing marginal utility. Why, I keep asking, does this not work in my classes? When I moved to my AP Government class later in the day, I enthusiastically discussed the Federal Budget process. I compared it to the realities of today, discussed progressive taxation, explained the current debate about reigning in Wall street abuse. I discussed the many important and fascinating issues that make this topic so important in our lives. I was pumped, energized, really on my game...and then I looked out and saw the most amazing example of Diminishing Marginal Utility. An increasingly slower demand for knowledge as the day went on. I guess I am too good an economics teacher. Where were you today my future Americans for Reason and Truth.