Everything has a downside—even optimism. In a new study published in Psychological Science, researchers asked hundreds of football fans to predict the outcome of each game of the 2008 NFL season a week before it was played. They found that fans always predicted an above-average probability of success for their favorite teams, no matter how poorly the teams had performed in previous games. Some of the most important decisions we make—such as whom we will marry—rely on our ability to predict the future, one of the researchers explained. Accounting for the negative effects of optimism might not make these predictions any brighter, but with any luck it will make them better.