Think of emotion and reason as two variables responsible for decisions and beliefs having an inverse relationship, that is, the more you rely on emotion the less rationality is needed to support/justify your decision or belief. For example, the more emotionally invested one is in a potential home, the less concerned one is about problems such as termite infestation, being way overpriced, and the severed heads buried under the kitchen floor.
Keep this in mind when you hear arguments, see commercials, listen to politicians, read articles in the media, and accept information from anyone. As a general rule of thumb, the greater the emotional appeal being made, the more skepticism one should apply to the claim. Or to put another way, arguments heavy on emotion are usually light on facts and evidence.