There's a great quote from Alice in Wonderland - “If you don't know where you are going, any road will get you there.” Having a vision gives your business some sense of direction. If you start with your vision you can plan the road map for getting there. There will be holdups and detours on the way, but knowing your destination helps with the choices you need to make. It is also alright for that vision to adapt and change. Nothing is static, you change, your situation changes and the environment you work in changes. Revisit your vision and refresh it from time to time making sure that you are still moving forward with your business.