Just finished reading The Upside of Irrationality by Dan Ariely (highly recommended, just like Predictably Irrational). One take-away from this book: if you thought making decisions while under the influence of strong emotions was a bad idea, now there is hard data to back that up. It's worse than you thought, because those decisions affect your future decision-making patterns.
Side note: this book was a pleasure to read on the iPad.