We asked YC founders for their rookie mistakes, so we could share them with you and help you avoid them. Here's the next comment that was written by a YC founder. We built a product because we thought the world should be a certain way, not because we had a customer who actually wanted to buy the thing we were building. It's really hard if someone doesn't want something to like debate them, and convince them they do actually want it when they don't actually want it.