Answer:
The law of diminishing marginal utility
Step-by-step explanation:
Simply put, as more (additional unit) of a good is consumed the lesser the marginal utility or satisfaction derived.
For example, a child might request a certain type of chocolate form his parents for a period of time.
After sometime, the child may buy less and choose another type of chocolate or prefer to buy cake instead because the satisfaction he initially got from the chocolate is diminishing.