It could be, for example, the risk of a change in the economic environment - what are your contingency plans for that in terms of dealing with such a situation? There may be many other risks as well specific to your particular sphere of operation, but that ability to plan ahead for all scenarios makes for a robust business plan.
If you are someone who shies away from planning, or you don't like writing or preparing documents, nevertheless you are going to have to force yourself on this occasion. I say that because it is such a key document for the future success of your business, such a tool throughout its development to return and refer to.
Have you done your research? Do you really know that the people you will be targeting want your product / service, and crucially do they want it AT THE PRICE that you will be offering it at? Whilst confidence in your plan is fantastic, you must make sure that it does not lead you down a blind alley along a path that is not desired by your target market. Don't assume what customers want, do your research and make sure that is clear from the start in your business plan.
A valuable source of information about your business that may be required by third parties ; Improved use of your company personal resulting from participation in the business planning process ; Increased employee motivation ; Increased profits and sustained growth.