I have been putting together business plans for over 25 years and it is clear to me that the strength of its core rests solely on being able to execute the plan. Each year I approach business planning as an opportunity, rather than a burden. I would rather invest the time up front in mapping out the upcoming year, than leaving it to chance to dictate my strategy. While this may force me to think strategically as well as tactically, preparing a detailed business plan in advance enables me to identify the challenges in advance of actually facing them.
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.