Everyone always talks about confidence in believing what you do. I remember once going to a class in yoga where the teacher said that, spirituality speaking, if you believed that you had achieved enlightenment you have merely arrived at your limitation. I think that is also true in a practical sense. Deeply held beliefs of any kind prevent you from being open to experience, which is why I find all firmly held ideological positions questionable. It makes me nervous when someone believes too deeply or too much. I think that being skeptical and questioning all deeply held beliefs is essential.
Ten Things I Have Learned(MiltonGlaser.com)