A: What's for dinner?
B: I'm not sure.
A: How about a pizza?
B: You had pizza for lunch.
A: But I love pizza.
B: Everybody loves pizza.
A: So why can't I have pizza for dinner?
B: Because you need variety.
A: What's "variety?
B: Different things, not the same thing all the time.
A: You mean, like a pepperoni pizza instead of a cheese pizza?
B: No, I mean a salad instead of a pizza.