One topic that is seemingly overlooked, yet plays an important role in managing projects, is credibility.
Credibility is one of those abstract terms that is difficult to define but quite apparent when lacking. For purposes of this book, credibility is defined as behaving consistently with beliefs and expectations. Without consistency, a credibility gap can arise. Also, one's credibility will constantly be on trial. Credibility is very hard to get and very fragile. 
 James M. Kouzes and Barry Z. Posner, The Leadership Challenge , Jossey-Bass, San Francisco, 1987, p. 24.