A lifelong secret to understanding people. If we want to see through a person and know their true nature, we should not focus on what they think or say, but rather on what they have done, what they have experienced, what they have accomplished, and what they repeatedly do. This is because thinking and speaking come at zero cost; anyone can think wildly or say anything casually. However, doing—especially doing repeatedly—requires investment of one's life, which is a significant cost. This indicates that the person has clear intentions or strong motivation, making their actions more credible. What they do represents who they are. Therefore, the key to understanding people is to see if their words and actions are consistent. If there is a conflict between behavior and language, we are more inclined to trust the behavior.