If we are wise, then we never stop learning both our Art, and other things that supplement it. Instructors should always seek to constantly improve themselves and through self-awareness recognize their own strengths, weaknesses, assets, and limitations. Recognize your strengths and assets and exploit them. Find your weakness and limitations and conquer them. Be technically and tactically proficient.
Technical excellence is paramount for an instructor.
Constantly practicing to maintain and improve your skills is a part of the never-ending journey that is the Martial Arts. Again, this applies directly to the paragraph above. Seeking self-improvement sets the example for your students. Tell them you are not certain of the correct answer, and immediately seek to learn the correct answer. When you have the answer, get back to your student.