Cognitive scientists tell us that we are hardwired for deceptionoverly optimistic about outcomes. In fact, we surely wouldnt have survived without this trait. With this built-in bias as a starting point, its no wonder that software managers and teams almost always develop poor estimates. But that doesnt mean all is lost. We must simply accept that our estimates are optimistic guesses and continually re-evaluate as we go. Linda Rising has been part of many development projects where sincere, honest people wanted to make the best estimates possible and used scientific approaches to make it happenand all for naught. In many projects, because re-estimation was regarded as an admission of failure, the team spent too much time and endless meetings trying to get it right. Offering examples from ordinary lifeespecially from the way people eat and drinkLinda demonstrates how hard it is for us to see our poor estimating skills and offers practical advice on living and working with the self-deception that is hardwired in all of us.