1. If you can’t sell it, don’t build it.
2. If you can’t build it, don’t sell it.
It's a common thought that the single necessary and sufficient condition for a business is a paying customer. But that’s not a sufficient requirement for a good business. It's about finding the sweet spot of what is desirable to customers, technically feasible and commercially viable. Then we need to sell it, keep selling it and sell it some more. Great post by Mark Ridley.