"But you can't expect people to act rationally. We are emotional creatures."

Yes, we are emotional creatures. But being emotional is not incompatible with being rational! In fact, being emotional sometimes makes us more rational. For example, anger can inhibit some cognitive biases, and people who sustain damage to "emotional" areas of their brains do not become more rational, even when they retain memory, logical reasoning ability, and facility with language. What we want to do is make the best possible use of our available tools -- including our emotional tools -- in order to get the things that we really want.