In the first half of Act I, both Romeo and Juliet have potential romantic partners, but neither one is really satisfied. Romeo is literally unsatisfied because Rosaline has sworn a vow of chastity—and Juliet is unsatisfied because she's thirteen, and boy bands haven't been invented yet.
Romeo and Juliet meet and obviously fall immediately in love. There's a lot of flirting and love poetry—but don't get out the bon-bons just yet, because there's a major frustration stage ahead of us.
Romeo and Juliet realize that the person they just fell in love with is one of their greatest enemies. This is like … if the head cheerleader and quarterback from two rival schools fell in love: they want to be together, but everything they've ever known tells them not to trust each other. Can their relationship ever work?
Maybe in a romantic comedy—but this is tragedy, baby. Romeo and Juliet decide to get married anyway, but less than an hour after they say their vows, there's a big brawl and Romeo ends up killing Juliet's cousin, Tybalt. She forgives him, but he's banished from Verona … and Juliet's parents decide they want her to get married to Paris that very week. Eek!
Being forced to marry Paris is a fate worse than death, as far as Juliet is concerned. So, she fakes her own death. Pretend death becomes reality when Romeo hears the news of Juliet's death and believes that she is really gone. Minutes before Juliet is due to wake from her drugged sleep, Romeo comes to her tomb, kisses her good-bye, and kills himself. Juliet regains consciousness to find her husband lying dead beside her. When she kisses him, she realizes that his lips are warm and that she's missed him by a matter of minutes. In despair, she takes his dagger and stabs herself.