A business needs to have a clear sense of purpose if it is to succeed. This purpose needs to be articulated in a document that sets out the mission, vision, values, and unique selling proposition of the company.
Your mission, vision, values, and unique selling proposition (USP) are the foundation of your business. Your mission is why your business exists; your vision is how you want to serve your customer base; your values are what drive you towards continuous improvement. Your USP is what sets you apart from the competition and compels your ideal customers to do business with you instead of them. Articulating these things clearly and persuasively removes risk and allows you to break away from the noise.
Codifying your mission, vision, values, and USP is critical to the success of your business. Without it, there would be confusion and chaos, and progress would be impossible to achieve. This document will guide all decision-making within the company and ensure that everyone is working towards the same goal.
But of course, this needs to be a living document. These ideas might change very rarely, but fixing them in cement for all of eternity is a guaranteed way to make yourself obsolete as the market evolves over time.
As the business owner, be sure you are working with trusted partners who can help you stay focused on what you all have agreed upon when times are tough, but wise enough to help you make the right pivot when it's time to adapt to new information.