USER TESTING
Whether you are an ENTREPRENEUR or any type of leader or developer, keep in mind that plans are not requirements -- it is not only important to do things right, it is important to do the right things. I have never seen a plan so comprehensive that it covers everything the users of a product will think about.
USER TESTING is how we know what users or our product (whether our product is a physical object, a software tool, or an idea) will do with it, what they will find useful, what they will find useless, what they will find confusing, how they will interpret what we provide, how they will use it, if they will use it. USER TESTING will show us what we cannot possibly see ahead. Of course we should plan well but the real world is more complex than we imagine it and we cannot think of everything ahead of time.
Don't overcommit to your plans as requirements before you follow through. Include and pay attention to USER TESTING. The "shortcut" without USER TESTING will be a much longer route.