Why do people eat too much at buffets and drink too much at parties?

We have discussed and analyzed the choices of firms using marginal analysis. Let's apply the same kind of thinking to everyday life. Why do people tend to eat too much at buffets and drink too much at parties? Use marginal analysis in your answer. (Hints: (1) Marginal analysis is used to answer "how much" questions like should I eat another piece of pie for dessert; and (2) what is the cost of one more trip to the buffet and what do I gain?)