Make a plan but be flexible
You need a few sets of plans, even if each is only a few pages. A business plan, with an accompanying marketing outline, are important blueprints for success. They help you map out the major landmarks of the road ahead, define your success and break the journey into important metrics you can track your progress against.
I’m not one for a giant, robust plan nobody will access, but I do advocate a more modest go-to plan that can act as your basic instruction manual and hold you accountable to specific numbers. The reason I don’t support highly detailed plans is that I believe you need the flexibility to alter the course as necessary. Sometimes, large changes to the plan will be necessary.