I teach that you should seek to learn from competitors; obviously never copy another business's idea or what they are doing, but you can absolutely learn from their mistakes or see what they are doing and discover ways to improve it. All of that analysis belongs in your business plan: make sure you have your competitors under the microscope and make sure that is a solid chunk of your plan. That is some of the best research and information you will gather about what will make your business successful in future.
I often see people split into two camps. On one hand those who almost ignore competitors in their business plan, because they do not want to think about the issue yet and feel so confident they have a great idea for the market regardless. But I recommend not being overconfident when it comes to competitors. They are still there for a reason, they are still around and in business for a reason, so view them with that in mind.
It is known to be the most crucial step in the successful running of the business because a well planned business venture carefully scans all the possible opportunities and threats, understand the demands of the market and arranges for the best possible resources which finally lead to the success of the business.
You can concentrate so much on essential financials and supply logistics, but overlook other issues like marketing or opening times. By showing the plan to someone you trust, they can have a look and see what might be missing or worth developing more. Getting that valuable second opinion on how robust your idea is will put you in a much better position to start and keep going successfully.