Overindulgence of a good thing.
Eating too much makes you fat. Spending too much money makes you broke. Working too much leaves your family at home missing you.Playing too much leaves important work undone. And so on and so forth.
Happiness depends on the balancing act of applying your positive resources equally to the hungry deficits in your life. All details aside, the important thing to remember is this: Long-term happiness is never found in one good thing; it is a combination, it is a balanced lifestyle.