This chapter centers on Marcus Aurelius’s assertion, “Our life is what our thoughts make it” (127). Carnegie agrees with this concept, arguing that we can control our mental processes through a positive attitude. When faced with a problem, readers should cultivate concern instead of worry. Concern involves calmly assessing issues and planning how to resolve them. By contrast, worry is a waste of mental energy that resolves nothing.

The author states that mindset has a powerful effect on our physical state. For example, British psychiatrist J. A. Hadfield conducted an experiment on three men, testing their strength when squeezing a dynamometer. The men’s strength was tested in three different scenarios. Under normal conditions, their grip averaged 101 pounds. After being hypnotized and told they were extremely weak, they managed only 29 pounds. Finally, the men were hypnotized to believe they were extremely strong, and their grip increased to 142 pounds.

Carnegie also relates the story of Mary Baker Eddy, the founder of Christian Science. One day, Eddy slipped on ice and injured her spine so badly that doctors were certain she would never walk again. However, after reading the story of Jesus healing a man with palsy, she got out of bed and walked.