Heartbroken and lamenting. Romeo is wallowing in self pity after rejection from Rosaline - his initial love interest. He pines over her, through copious amounts of blazon (nature poetry) and onamatopeic phrases, coupled with aggressive verbs to emphasise the agony of love ('vexing, 'purging'). Basically, he's being incredibly dramatic and somewhat pathetic. Therefore, Benvolio suggests they go to the Capulet party to help Romeo get over his infatuation, but Romeo declares he cannot. Of course we know he does, as he immediately forgets Rosalind as soon as he sets eyes on Juliet.
