Thou shalt not say "No." If you don't like the suggestion, work it out amicably. Learn the art of compromise.
Thous shalt always communicate in a professionla manner. Listen to your client. Educate your client.
Thou shalt strive to constantly increase your expertise. Grow and learn; get it better than the day before.
Thou shalt relax and have confidence in yourself. Nobody's shooting at you, and you're not doing brain surgery on your mom. Believe in yourself and other will too.
Thou shalt make it a point to have fun. Love your profession. Do what you want; work where and when you want, and work with nice people only.
Thou shalt have a personal life. Never feel guilty about making (and taking) time for yourself and loved ones.
Thou shalt be hones and ethical. Never promise something you can't deliver. And remember: you are selling a product, not your soul.
Thou shalt be a good businesperson. Protect your rights by keeping abreast of the ethical standards, laws, and tax reforms. Stay current with pricing guidelines. Learn effective negotiation skills. Maintain excellent records. Don't start a project without paperwork.
Thou shalt not take rejection personally. A thick skin and the ability to bounce back are more than cliches in a field where you need those very attributes to survive.
Thou shalt never miss a deadline! Perhaps the cardinal sin. Be late with a job and chances are you will never be called again by that particular art director.