I recently read an article that stated there was evidence to suggest that the simple act of creating a Plan B would ultimately hinder your achievement of a Plan A (article here) and that got me thinking.
One of the traits I believe sets entrepreneurs apart is their ability to quickly make the best of a bad situation or turn a bad situation around. They analyse at thought-speed, decide instantaneously and set about the activity that will lead to the outcome they want.
So, if the article is indeed true that the simple existence of a Plan B increases the chances of Plan A failing then think like an entrepreneur and 'know' that whatever happens to Plan A, you will make the best of it. You will find the silver lining and reach your success.
Create your Plan A and then put the blinkers on, focus on the execution of that plan, review accordingly, make the necessary adjustments and get back to work on Plan A. What you'll also find is that there never is a Plan B, just a reworked Plan A, improved with the new data.