Anyone else realize the customer you wanted isn’t always the customer you need?

When I started I had a very clear picture of who I wanted to build for. I spent a lot of time thinking about that ideal user and what they would want. Then real customers started showing up and some of them were completely different from the people I had in mind. Their problems were different too and honestly they were the ones paying the bills. At what point do you stop trying to find the audience you imagined and start building for the one that actually showed up?