Building a product-driven business takes energy. There’s marketing to generate interest, and a sales apparatus to bring deals home. On the product side, there’s the initial user experience to develop, and the value your product should demonstrate from the get-go.

These activities are all important for getting customers in the door. But once people start using your product, it’s your retention strategy that keeps them there. Plenty of users are willing to try a product once or twice. But if your product or feature doesn’t provide ongoing value over time, or is too difficult to use, or if the pains your product addresses can be more easily solved by a competitor, those users won’t stick around.

In fact, from a product perspective, it’s not unreasonable to say that retention is the best measure of product-market fit. For the bulk of digital products—websites, mobile apps, business platforms, and many more—achieving product-market fit means producing a product that users willingly return to.