Big decisions are hard. We consult friends and family, make sense of confusing "expert" advice online, maybe we read a self-help book to guide us. In the end, we usually just do what feels right, pursuing high stakes self-improvement--such as who we marry, how to date, where to live, what makes us happy--based solely on what our gut instinct tells us. But what if our gut is wrong? Biased, unpredictable, and misinformed, our gut, it turns out, is not all that reliable. And data can prove this.