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.
Did you ever stop and think what a unique position you're in as a business owner? I don't know of any other way you can have as much control over your success than owning a business. When you work for someone else, you are totally at their mercy as to what your future may be like. It doesn't matter whether it is a private business you work for or a large corporation. Your future is in their hands. The only thing that might qualify other than owning a business would be to inherit or win a lot of money that would give you everything you want in life.