Evaluate yourself from time to time. Do you measure up? If you don't, admit it, then correct the problem. On the other hand, don't sell yourself short. If you think that you are the best in a certain area, say so. Then set out to be the best in that area. Learn how to speak effectively, how to instruct and how to be an expert in the area that you hold the knowledge in. Not everyone who is an expert has the communication skills in order to teach others. These communications skills takes practice over a period of time. Volunteer to speak in public when given the opportunity.