What is your biggest regret? It’s a tough question to ask yourself. Not many people are brave enough to admit they have regrets because it means acknowledging that not everything is like they would want them to be. That’s hard to do for one reason: we all like other people to think that we live perfect lives. In a unique social experiment, New York City passersby were asked to write down their biggest regrets on a huge chalkboard. As the board filled up, there was one answer that seemed to repeat itself. You’ll be surprised to find out what it was.