When presenting your business plan to an angel investor you must understand that they will be very interested in your spreadsheets and proformas, but you must also realize that it is typically an entrepreneurial optimistic approach, which causes problems with proformas. Therefore, you should have dueling spreadsheets; that is to say the spreadsheets, which take your best guess and double the time, double the expenses to compete with your optimistic approach. You should be able to present both of these to your Angel Investor; who chances are is a retired business person with a little bit of financial savvy.
Most people are aware of the benefits of a personal health check and will not think it unusual to have one carried out periodically. It does therefore appear strange that the same people do not carry out a health check on their business. In the same way as an individual will benefit from a personal check so a business will also benefit from an early diagnosis of potential problems. In general the later a problem is identified the more drastic, painful and expensive is the solution to the problem.