Set yourself a reminder to review your business plan regularly. If you have a team in your business, holding brainstorming sessions is a good way to benefit from their knowledge - it ensures you are all on the same page and that you get their support.
Start from the very beginning understanding that your business plan ought to be specific to your business needs and objectives. Every business ought to have a plan, but not every business needs a full formal plan with carefully crafted summaries and descriptions.
A business plan is a blueprint for how your business will run and reveals what future direction your business will take. Understandably you will want to be careful who you show your plan to and avoid your competition seeing it.
If you don’t have a specific immediate need to show a formal business plan to a banker or investor, then you are probably better off doing just a lean business plan, for your internal use only. To make the best impression on banks and investors, your business plan outline should be presented in the standard business plan format.