I spent almost five months building my SaaS without a single paying customer. People were signing up. Some of them even used the product. Nobody paid. Like a lot of founders, I convinced myself the answer was just one more feature, one more improvement, one more week of building before it would finally be "ready." Then I noticed a user who had signed up about a week earlier and quietly disappeared. Normally I would've assumed he'd lost interest and moved on. Instead, I sent...