The author's purpose is to show that you are responsible for success or failure in your own life.
Explanation:
The author shows that the work we do and the way we develop it is responsible for our success or failure in the activities we participate in. The author affirms that this is a good thing, because you will not depend on the actions of other people to influence your life, you will have to strive for your own success and if you fail you will only have yourself to blame, but this "guilt", allows you to fix your mistake and move on.
