The belief about life that is being described in this excerpt is (B.) individuals who follow their dreams eventually attain them.
These words were written by Henry David Thoreau, an American poet who lived during the 19th century and was best known for his essay "Civil Disobedience". In this famous quote, he makes reference to his formula for a successful life. He believed that when a person focuses on achieving his/her dreams and the life he/she wants to life, success eventually comes ("if one advances confidently in the direction of his dreams (...) he will meet with a success unexpected in common hours"). For Thoreau, it was very important to psych oneself up in order to reach goals.