Every profession has them. Some foolish beliefs that are shared by many, but for some reason or another, do not work. It is hard to say what is truth and not, especially if the myth applies to so many situations, and makes it harder to disprove. However, these are lucky moments, and certainly do not work for every situation out there.
Many of these myths are broken by common sense. Some of them through experience. What most of them have in common is some strong hold to ignorance. Somehow there is a desire to not be educated by experience, or observation. Perhaps it is due to some perceived reality that blinds those who believe in them from the truth.
In reality, good work takes hard work. Most myths are designed to short circuit this belief in an attempt to do it better, faster, cheaper, and/or easier. This is not to say that anything that makes things easier is to be considered a myth. It is the things that do not work that defeat the purpose of the thing at all.
So, how does one defeat myths? Learn from examples. Learn from experience. Allow yourself to be open of mind and willing to learn from failure, rather then be mad at your actions. Being a life long learner is extremely important.
Myths are heeded by those who wish to be disillusioned. People who wish not to be responsible for their own actions, and have a narrow view on the world. They are the people whom should not be trusted with that with you cherish.