It means one of the secrets of success is the ability to understand people well. Which could also translate to having a high EQ (Emotional Quotient).
Explanation:
The success being talked about here is not only Financial but also Individual/Personal success (i.e when a person is generally happy and feels fulfilled).
Seeing things from the other person's view point helps you to understand why he/she behaves thinks and reacts to things the way they do. When you understand other people's emotions as well as your own, you : are able to make better, objective and intentional decisions in every aspect of your life, whether personal or at the workplace; become more confident; and have healthier relationships. This brings all-round success.
