My biggest mistake as an entrepreneur is starting with an idea or a technology rather than a specific customer and their problem. The consequence of these mistakes is making products that people don't care about.

It's much better to start with a specific customer because you know who they are; you can talk to them, understand their needs, identify real problems, and quickly validate your assumptions. It grounds you in reality, helps you find truth faster, and makes it easier to make something people want.

Many entrepreneurs have expressed similar views.

Most people think first of what they want to express or make, then find the audience for their idea. You must work the opposite angle, thinking first of the public. You need to keep your focus on their changing needs, the trends that are washing through them. Beginning with their demand, you create the appropriate supply. Do not be afraid of people's criticisms—without such feedback, your work will be too personal and delusional. You must maintain as close a relationship to your environment as possible, getting an inside "feel" for what is happening around you. Never lose touch with your base. — If you can just learn to think about the market first you will have a big leg up on most people starting startups.

— 50 Cent via Sam Altman Lecture

There are many ways to center a business. You can be competitor focused, you can be product focused, you can be technology focused, you can be business model focused, and there are more. But in my view, obsessive customer focus is by far the most protective of Day 1 vitality.

— Jeff Bezos 2016 Letter to Shareholders

I tell every entrepreneur I know; Don't fall in love with the idea, fall in love with the problem. You're going to dump your idea the minute you realize its flaws.. But the problem? It's only going to get richer, more interesting, and more nuanced the more you learn about it.

— Marc Randolph

One of the things I always tell startups is a principle I learned from Paul Buchheit: it's better to make a few people really happy than to make a lot of people semi-happy. I was saying recently to a reporter that if I could only tell startups 10 things, this would be one of them.

— Paul Graham

It's even better to start with a very narrow group of specific customers. The smaller and more focused the group of people, the easier it is to build something uniquely delightful and to dominate that niche before expanding.

Most great companies start out with laughably small groups of specific customers.