Romeo has recently been dumped by his girl, and he is moping around and not really looking for another. Yet when his friends bring him to a party, he sees Juliet and everything changes.
When Romeo is first introduced, he tells his friend Benvolio that “sad hours seem long” become his girl, Rosario, has dumped him. The hours are long while he is out of the lady’s favor. Romeo compares love to smoke and “madness most discreet” (Act 1, Scene 1, enotes etext p. 16). He is in deep pain.
Romeo’s friends think it would be good for him to go to a party, to give him “other beauties” to choose from. Romeo resists, saying that he has “a soul of lead” and is too fresh from Rosaline to look at other girls.
I am too sore enpierced with his shaft(20)
To soar with his light feathers; and so bound
I cannot bound a pitch above dull woe.
Under love's heavy burden do I sink. (Act 1, Scene 4, p. 26)
Yet Romeo desperately wants someone to love. It does not take long before he sees Juliet and falls in love instantly. He is on the rebound, as we’d say now. Romeo is in that vulnerable period where his girlfriend has left him and he is feeling lonely and depressed, and more prone to rash decisions.
Romeo’s situation is one in which many people find themselves. Was Juliet love at first sight? Was Romeo just more susceptible to flights of fancy and more vulnerable to love? If Shakespeare’s prologue is to be believed, Romeo and Juliet were star-crossed lovers and would have found each other no matter what.
Page numbers from the pdf here: http://www.enotes.com/romeo-and-juliet-text