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.
As a matter of fact, did you know that the Small Business Administration says that 50% of small business owners will fail sometime during their first 5 years? There are lots of reasons but one big one is that owners don't have a plan. Another is they have picked a product or service that doesn't have a big enough market to sustain their business and sometime during their future they will run out of customers.