Haven't you ever heard rich girls can't marry poor boys?
When Nick finds out this information about Tom and Myrtle he is faced with a self conflict. Nick will have to decide if he wants to tell his dear cousin ,Daisy, that the man she is married to is cheating on her, or if he should keep this secret to himself.
Gatsby tries so hard to fit into society. When Tom criticizes his car this just makes Gatsby feel even worse about achieving his dream.
When Gatsby tells Daisy he loves her earlier in the story, her response breaks his heart. Not only is the girl he likes crushing his dream of being in love, but she is also breaking his dream of being in the elite society by reminding him of his real true self.