The story of The Little Prince has many moral lessons. As the Little Prince journeys from planet to planet and meets the residents who live there, he learns a lesson from each. For example, from the king he learns the futility of power; from the conceited man he learns the vanity of praise; and from the tippler he learns the destruction of shame. He learns that many people live meaningless existences that produce little benefit for others. But when he reaches Earth, he begins to learn lessons that impact him personally. Seeing the thousands of roses that look just like his rose makes him feel as if he was duped by his flower; she had told him she was unique, and he had believed her. The fox teaches him what it means to be tamed, and he realizes that his rose truly is unique: She has tamed him, and he has tamed her. The fox, as his parting gift to the Little Prince, shares his secret with him.
"And now here is my secret, a very simple secret: It is only with the heart that one can see rightly; what is essential is invisible to the eye."
The fox explains that one becomes responsible for what one has tamed, and the Little Prince realizes that he is responsible for his rose.
The main lesson, then, is that the meaning of life can be found only in relationships. Loving someone causes you to commit yourself to another, and that makes even the most humdrum occurrences of life take on deep significance.