Most people wouldn't think of building a house without a set of building plans. Without a building plan, it is doubtful your foundation would be adequate, you might forget key parts of the plumbing, and your kitchen might end up where your bathroom should be.The same situation will happen if you don't create a business plan. While you might think that you can keep everything in your head, your results are likely to be disappointing. The business plan process helps you think through all parts of your business, establish a solid foundation, and puts you in a position for business growth. The parts of the business plan that you can't do or are hard for you, are the areas where you need professional help. A plumber building his own house hires experts in roofing and other unknown areas. You need to approach your business the same way.
There are many business plan tools to help you - ranging from a workbook with simple questions to answer, to workbooks that help you create a detailed plan, to software with "fill in the blanks". These tools are similar to a house building plans - you can purchase ready-to-go plans if you are building a cookie-cutter house. You can also create custom plans, but that will take you more time. You need to decide the tradeoff between time and proper planning for your business.