Incidentally, the idea of working with a business plan is for one to keep focus on his set goals. Statistics has it that many businesses fail due to inadequate planning. If one doesn't know where he's heading to, any route seems to be the right one. Most people make great mistakes by jumping into business without adequate preparation and planning. A good business plan helps one maintain focus on his goals and execute the strategies that the plan assisted him in creating. Just like a road, one's business plan has to be consulted to make maintain his focus and not running business in a layman's way.
By making a business plan, you can pick out any potential flaws that might hinder you. It's a good chance to find any problems or issues that may arise, and then deal with them accordingly before you get caught up in the business. Also, outside parties can cast a fresh eye over the plan, and may pick out something that you may not have spotted.