As importantly, it also identifies road blocks - in advance. Your business plan should provide a common vision supported by tactical initiatives that, ultimately, creates greater value for your company. It may seem daunting, but by knowing your vision and its corresponding financial targets, you will have a better chance at executing how to get there and avoiding traps in advance.
Compartmentalizing your plan by developing planning modules allows you to attack the plan in parts, yet still maintain a cohesive plan. I have found that developing an annual plan made up of quarterly targets - thus becoming a rolling quarterly forecast financial model - allows for a cohesive structure along with the nimbleness to react to market conditions. At the end of each quarter, a true-up process to align results to annual targets needs to be re-forecast and adjustments made.