The moral lesson of the book is that love is all important.
The Little Prince sadly leaves his asteroid when the rose he loves becomes too difficult for him to deal with. He fears she is not quite honest with him. She tells him, however, that she loves him.
Although the Little Prince has adventures exploring the galaxy, he is still thinking about his rose when he meets the pilot. He tells the pilot that loving the rose makes him happy and that worrying about the rose being eaten by the sheep makes him sad. He is upset that the pilot doesn't seem to take this love and grief seriously.
Later, the Little Prince sees a garden full of roses just like his rose. He is deeply saddened that his rose, which he thought was precious because it was unique in the universe, is only one of millions of roses just like it. She is common. He begins to cry, but then, from the fox, he discovers that what creates love is not the uniqueness of the beloved but the relationship that bonds the lovers. What matters...
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