Most businesses require both an inside person and an outside person. The skills and personality required for each are quite different, and they seldom reside within the same individual. As a result, the business owner is likely to be much better at one than the other...and therein lies the problem.
One of the mistakes I most frequently see in business is owners not making a clear distinction between their ownership position in the company and the role that they fulfill, and this can be very damaging. As an owner, you should be paid a salary for what you do and get a return on what you own. You should be paid for the job that you actually perform and the financial reward for your ownership will come as a return in the form of profits and growth in the value of your equity. 
While partnerships can deliver great value in running an organization, the behavioral styles of the partners are often very different. This can lead to irritation and confrontation that not only puts a significant strain on their relationship but also damages the culture and effectiveness of the company.
John Lennon and Paul McCartney were one of the most successful song writing partnerships in history. They worked together for a period of about seven years and were driven apart by their success and their egos. From a business perspective, the inherent flaws in their business relationship provide an object lesson on how not to structure a partnership.