law of diminishing marginal utility

A psychological generalization that the perceived value of, or satisfaction gained from, a good to a consumer declines with each additional unit acquired or consumed.

Even the most delicious food, for example, will appeal less and less to its consumer when he or she has had enough, and if consumption continues, sickness (disutility) will result. Consumers deal with this phenomenon by consuming a variety of goods rather than lots of one good.