Two insightful and related quotes from one of the greats:
Have the courage of your knowledge and experience. If you have formed a conclusion from the facts and if your judgment is sound, act on it--even though others may hesitate to differ. You are neither right nor wrong because the crowd disagrees with you. You are right because your data and reasoning are right.
In the world of securities, courage becomes the supreme virtue after adequate knowledge and tested judgment are at hand.