What does this quote mean from Romeo and Juliet, and why does he mention Cupid?
ROMEO: Well, in that hit you miss: she'll not be hit
with Cupid's arrow, she hath Dian's wit;
and in strong proof of chastity well arm'd (I,i)
In the play Romeo and Juliet by William Shakespeare, the author portrays Romeo as what he really is - still a young boy approaching full manhood. He is starting to explore the world of love, of girls and of peer group dynamics - just like the young kids of today. In this scene, Willaim Shakespeare shows him at his most juvenile - wrapped up in himself, the things he cannot have and all the moods, sulks and withdrawal behaviors that go with those. He is sulking because he is suffering froman infatuative love sickness - and Rosaline does not "love" him back. Shakespeare mentions Cupid because this is not real love. Romeo is angry because she will not give him what he wants - Cupid (who represents love) has missed her with his arrows of desire.
In this scene, Romeo is complaining about how Rosaline does not love him. This is before he meets Juliet and falls in love with her.
What the quote means is that it is impossible to get Rosaline to fall in love with him. He mentions Cupid because of the old legend that people fall in love when Cupid shoots them with a bow and arrow.
He says she cannot be hit by Cupid's arrow because she is too smart -- like Diana. Also, she is armored by her chastity and that protects her from Cupid's arrow as well.
The first part of the quote is just Romeo's reply to what Benvolio has said about it being easier to hit a "fair mark."