The most common mistake early-stage builders make is asking people what they want and believing the answers. People are notoriously bad at predicting their own behaviour. They say they would pay for something, then do not. They say they want a healthier option, then choose the familiar one. They say they would switch products, then never do. The reliable signal is not what people say — it is what they already do. What do they spend money on without being asked? What do they search for without being prompted? What do they complain about consistently? Where do their current solutions fall short enough that they seek workarounds? These behaviours are the evidence of genuine desire. Build toward the behaviour, not the stated preference.