V Mary Abraham published a great post called "Do rational people work at your firm?" where she asks why we make so many bad decisions despite that we "pride ourselves our ability to make logical decisions". She presents a number of compelling examples of bad decision making, such as that people "routinely vote against their economic best interests in support of positions that have little impact on their lives". She suggests that we make these bad decisions "because our decision-making capacity is limited by our knowledge and self-awareness".
I agree. I especially agree with the self-awareness part, because I think that the main reason why we make bad decisions is that we think that we are rational beings, when we actually aren't. We need to recognize that we are first and foremost emotional beings. Human beings are certainly more rational than dogs, but just because dogs are 100% emotional and we are more rational than dogs doesn't make us into rational beings. The problem is we don't want to accept this (if you would tell a person that he or she is not acting rationally, you would probably get a very emotional response back).
That is also why using only rational arguments is not enough when trying to convince people. You have to speak as much (or even more) to their hearts as to their minds. When you do, you can even make them vote against their own best interests.