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.
In many cases business plans are very important but so much of the time it is a plan to try to convince someone else that you know what you are doing with your business like banks, investors, partners, etc. Now it is true that a well written business plan can also be a major benefit to your success as well if done right. It can guide you and keep you on track and can be the vehicle to get you were you want to be especially with so many outside forces now days that bombard you. A plan can be extremely important to your success especially when you look at the statistics that says 51% of small businesses fail sometime during their first 5 years.