Juliet spends much of her time in Romeo and Juliet in desperation; therefore, that is the characteristic that I choose to focus on for my answer. In truth, Juliet becomes desperate even before there is truly anything wrong. She even hints at this characteristics while waiting from news of Romeo from her nurse:
The clock struck nine when I did send the nurse; / Perchance she cannot meet him. That's not so. / O, she is lame! (2.5.2-4)
Juliet is already desperate: desperate to hear from her lover. Her desperation gets worse of course with her words to Friar Laurence as her situation declines:
Be not so long to speak. I long to die / If what thou speakst speak not of remedy. (4.1.68-69)
Juliet's lover has killed her cousin and has been banished from Verona. Juliet is betrothed to Paris, whom she does not love. Desperation ensues. (The sad thing is that Friar Laurence's suggestion is to give Juliet drugs that make her look dead!)
Of course, Juliet's biggest bout of desperation is at the end of the play:
What's here? A cup closed in my true love's hand? / Poison, I see hath been his timeless end. / O churl! drunk all, and left no friendly drop / To help me after? I will kiss thy lips, / Haply some poison yet doth hang on them / To make me die with a restorative. /Thy lips are warm! / . . . / Yea, noise? Then I'll be brief. O happy dagger! / This is thy sheath; there rest, and let me die. (5.3.168-174)
There is no greater act of desperation than to take ones own life. Thus, the tragedy of Romeo and Juliet lives on.