Say "No"
Product people tend to be optimists. That's not surprising; it's their job to identify solutions to problems. But the best product people also know when not to solve a problem.
I recently wrapped up a project in which we evaluated how the client might bring a new product to market. On its surface, the new product seemed like a clear extension to the company's main offering that they'd been selling since their founding. It was based on expertise the company had already garnered over years of blood, sweat, and tears. It was a product that solved a problem their current customers have. In fact, for which many of their existing customers were already asking my client for a solution!
BUT during our product discovery work together, we learned things that gave us pause: supporting the product would require the company to hire new staff with very different skill sets from the people already working at the company, and - though the customers might be the same companies they were already serving - we learned that pricing for the new product could actually hurt relationships with current customers.
The new product was in an exciting space, but my client still made the tough decision not to pursue it. Though it was in a fast-growing market, it was also one with many unknowns, and our product was likely going to require significant investment before achieving success. The only way my client could come to this decision was by spending time to understand the problem, its potential solutions, and how they fit with the company and its market. Budgeting the time to do the research and discovery up front meant they couldn't get started on the shiny new product, but it also let them avoid what would likely have been a very costly mistake.
There's a world of opportunity out there. I like to think that every time you say "no", that frees you up to say "yes" to something else.