Writing a business plan can be intimidating. I've talked to multiple business owners who are terrified at the prospect of writing business plans (usually for business financing) because it's hard to imagine writing down, in a logical sequence, how the business runs.
Before you know it, you'll have a working business plan. Just edit and format as needed.
And I do recommend that you continue adding to your business plan as your business grows and changes. Having a living document that grows with your business will give you (and anyone who has access to it) better context on where your business is coming from and how it changes for the future.