How does affect a person's career planing? give two reasons in detail

The question is this, how does self knowledge affects a person's career planning.
Self knowledge is defined as having a knowledge of oneself; that is, possessing a very clear and accurate perception of whom you are and what you are capable of doing. This self knowledge is the foundation on which a successful career should be built.
If you know yourself very well, you will know your strengths, abilities and characters and this will guide you in choosing a career that complement your traits and in which you have interest.
Choosing a career you have passion for will give you a great leverage to succeed in your chosen career and to accomplish much in little time.