focus on the boring stuff: how to measure progress, how to set up milestones, and how to prioritize work. - Eric Ries

If we do not know who the customer is, we do not know what quality is.

The question is not “Can this product be built?” In the modern economy, almost any product that can be imagined can be built. The more pertinent questions are “Should this product be built?” and “Can we build a sustainable business around this set of products and services?

Remember, planning is a tool that only works in the presence of a long and stable operating history. And yet, do any of us feel that the world around us is getting more and more stable every day? Changing such a mind-set is hard but critical to startup success.