In many cases business plans are very important but so much of the time it's a plan to try to convince someone else that you know what you are doing with your business like banks, investors, partners, etc. Now it's true that a well written business plan can also be a major benefit to your success as well if done right. It can guide you and keep you on track and can be the vehicle to get you were you want to be especially with so many outside forces now days that bombard you. A plan can be extremely important to your success especially when you look at the statistics that says 51% of small businesses fail sometime during their first 5 years.
As an example, let's say your current average number of transactions per month per customer is 3ǌ. Which says on average each customer does business with you 3 times each month. You could calculate how much more profit you would get if you could increase it to 3Ǒ. And I can tell you that would probably be enough to meet your plan. And if that did generate enough profit, all you would have to do is maintain everything else; sales, expenses, labor, average dollar sale, etc, and then just figure out how you could increase your transactions from 3ǌ to 3Ǒ. Maybe it could be with some type of promotion that would get customers to come in more often.