For professional people, having confidence in ones work is very important. However, confidence may also be described as a type of presumption. When you are overly confident, you tend to assume that your work (or your part of a project) contains no problems, and therefore that any issues must have been caused by others. It is all too common to well-meaningly involve all related parties when a problem arises, only to realize that you were in fact at fault and be forced to apologize. Therefore, while confidence is a necessary quality for professional people, this is a double-edged sword, as confidence can also be the cause of problems too.
