In act 1 of Romeo and Juliet, Romeo reveals himself to be melancholy, self-centered, and highly changeable. As the play opens, Romeo is in love with a woman named Rosaline who has refused his love. Therefore, Romeo is moping and miserable. “Griefs of mine own lie heavy in my breast,” he complains. “I have lost myself,” he continues, adding, “I am not here; / This is not Romeo, he's some other where.” Rosaline has scorned him. She is “too fair, too wise, wisely too fair,” Romeo explains, and she has sworn not to love anyone. Therefore, he laments, “in that vow / Do I live dead that live to tell it now.”
Indeed, Romeo is far more caught up in his own feelings than he is in Rosaline. He is focused on himself even as he thinks he is focused on her. He is focused on how wretched he feels. “O, teach me how I should forget to think,” he exclaims to Benvolio, who wisely tells him to look at a few other women. Romeo doesn't think that will work, for other women will only remind him of how beautiful Rosaline is. Actually, Romeo doesn't really want help. In fact, he seems to rather enjoy his suffering.
Yet when Romeo catches sight of Juliet, he forgets all about Rosaline in an instant (so much for being truly in love!). “O, she doth teach the torches to burn bright!” he exclaims. Then he asks himself, “Did my heart love till now? forswear it, sight! / For I ne'er saw true beauty till this night.” At this point, Romeo doesn't even know who Juliet is. He just sees her and instantly loves her. We wonder, of course, if Romeo has any idea what love actually is since he can drop one woman (the woman he claims to love to the point to obsession) and quickly become enraptured with another. Indeed, he is changeable and quite shallow. He thinks he feels deeply, but his emotions are primarily on the surface, and they will lead to tragedy.