Startups exist not just to make stuff, make money, or even serve customers. They exist to learn how to build a sustainable business. - Eric Ries

When people are used to evaluating their productivity locally, they feel that a good day is one in which they did their job well all day.

It is also the right way to think about productivity in a startup: not in terms of how much stuff we are building but in terms of how much validated learning we’re getting for our efforts.

Do consumers recognize that they have the problem you are trying to solve? 2. If there was a solution, would they buy it? 3. Would they buy it from us? 4. Can we build a solution for that problem?