How essential is planning? Having a goal is essential for success, because obviously without goals we couldn't measure success. The more detailed we craft our goals to be, and the more detailed we are on constructing the steps necessary to acquire the goals, the "better" the plan may be.

However as I have learned, a plan is comparable to a road map, or this day and age GPS. It's good to help navigate, but sometimes detours from the planned route or GPS instructions are necessary.

So my questions are very open ended, but I hope you will answer with your personal business operating/planning experience.
How important is business planning to your business? What are your main areas of focus anytime you create a plan? How often do you stray from your plan?

Knowing what you know now, what areas of planning do you wish you would have focused more or less on when starting-up?