There is an economic law that states that the utility of any good
declines the more one consumes of it. In other words, the more we have of a good, the less we desire it. This is referred to as the
"law of diminishing marginal utility." A person who likes pizza
will receive some utility if he eats a slice of pizza for lunch. If he
eats a second piece, it provides less utility than the first one. A
third piece of pizza provides still less. Eventually, the cost of a
slice of pizza would exceed its marginal utility and the person
would not purchase more