It's hard to see your customer with your idea in the way.
Sometimes, you haven't realised you're at your destination because you haven't put your map down.
In the same way, your ideas and preconceived notions block your ability to see people who would be great customers and what would make great products.
When I had an internet cafe business, my business partner signed up a hotel as a customer. I thought it was a distraction; it didn't fit our marketing plan which targeted coffee shops. I thought we should focus.
Well, that one hotel made more money than the rest of our coffee shops put together. So we switched the marketing plan to focus on hotels.
A lot of tools work well when filled with real information - business plans, business model canvases, personas.
But when you use these tools to write fiction, they prevent you from seeing the real need and real opportunities.