A movie director friend of mine one told me that it is customary to say that every movie actually is made 3 times: first when you write the script, then when you shoot it and finally in post-production.
I like to think of the same metaphor when thinking about businesses: you build the business on paper first, then you validate it with your customers, and finally you need to build yet another company that can withold the internal and external pressures of an organization at scale.