Sometimes there is dissent among partners on the direction that the company should go and how the business should be run. It is best to work these details out up front if possible. Once the company is started, you must support its commitments. You may have to turn down promising job offers because you have commitments to the company and to clients that would not be fair to back out on. I have canceled vacations and worked on the floor of airports to meet client deadlines.
Every business has to be marketed.
I usually carry business cards and brochures in case a marketing opportunity arises. I sometimes have to force myself to follow through on business leads. If you devote all of your attention to one client, you may find yourself without any work when that client is on a down business cycle. I know a business owner who turned down several other clients and canceled a vacation to help his main client through a poor planning initiated crisis. The project was pulled out on schedule and under budget and the deliverables received positive reviews.