What we have here is a "Boy Meets Girl" story. In the beginning, Leo is somewhat reclusive, perhaps even regressive. He lives with his mother, and he is a passive person. He is deeply passionate, and so there is a confusing dilemma in his decision making. On the one hand, he is positive that he does want something out of life, but his life is defined by indecision and procrastination.
Then he meets Mardou, and everything changes. She serves him in a way, by being so beautiful to him, so cherished and precious to him, and he realizes that if she could love him, that it would be enormously helpful to him. For once, he knows with confidence that there is something worthy of risk. He is overwhelmed by his desire to impress her, and she brings him to his full fruition. In response, she realizes the depths of her desirability by watching him grow to impress her, and she falls for him.
This portrait seems one way to the characters, but the reader can see with a bird's-eye view, noticing that there is something instinctual about these things. Although Leo thinks it is lofty passions that draw him toward Mardou, it is secretly animal instinct compelling him, and he simply experiencing it from his lofty point of view. This is evident in Roxanne's criticism, because she notices that he has sacrificed writing. Leo knows why the sacrifice works—he was only ever writing about his hopes of encountering someone like Mardou.
