CHORUS The fearful passage of their death-marked love […]
Is now the two hours' traffic of our stage; (Prologue.9, 12)
Well, you can't get much more transient than two hours, right? Love, sex, and death all in about the time it takes to watch an average-length movie.
Act 1, Scene 5
CAPULET Welcome, gentlemen. I have seen the day That I have worn a visor and could tell A whispering tale in a fair lady's ear, Such as would please. 'Tis gone, 'tis gone, 'tis gone (1.5.25-28)
Lord Capulet's musings about the good ol' days reminds us that youth and love are fleeting. This occurs just before Romeo and Juliet's first meeting, where they fall head over heels in love (at first sight). It seems like Lord Capulet's reminiscence is Shakespeare's way of preparing us for the short-lived (no pun intended) romance between Romeo and Juliet.
CAPULET Nay, sit, nay, sit, good cousin Capulet, For you and I are past our dancing days. How long is 't now since last yourself and I Were in a mask?
CAPULET'S COUSIN By 'r lady, thirty years.
CAPULET What, man, 'tis not so much, 'tis not so much. (1.5.35-40)
Here's a good look into the future: Romeo and Juliet might be in l-o-v-e now, but how would they feel after a decade and a couple of kids? Probably not spouting so much love poetry.
Act 2, Scene 2
JULIET […] Although I joy in thee, I have no joy of this contract tonight. It is too rash, too unadvised, too sudden, Too like the lightning, which doth cease to be Ere one can say 'It lightens.' Sweet, good night. This bud of love, by summer's ripening breath, May prove a beauteous flower when next we meet. (2.2.123-129)
Juliet claims that she's frightened by the sudden power of her and Romeo's love, and she's worried that it will burn itself out. She decides to say goodnight to him to prolong their love until their next meeting. Hmmhmm. Sounds like someone's been reading The Rules.
ROMEO Lady, by yonder blessèd moon I vow That tips with silver all these fruit-tree tops—
JULIET O, swear not by the moon, th' inconstant moon, That monthly changes in her circled orb, Lest that thy love prove likewise variable. (2.2.112-116)
Juliet's right—much better to swear by the stars, which at least are constant. (If equally cliché.)
Act 2, Scene 3
FRIAR LAURENCE Holy Saint Francis, what a change is here! Is Rosaline, whom thou didst love so dear, So soon forsaken? Young men's love then lies Not truly in their hearts, but in their eyes. (2.3.69-72)
The Friar thinks Romeo's love is meaningless because it is so changeable—just days ago, Romeo was supposedly in love with Rosaline but now he wants to marry Juliet. But that does that automatically mean it's not real this time?
Act 2, Scene 6
FRIAR LAURENCE Here comes the lady. O, so light a foot Will ne'er wear out the everlasting flint. A lover may bestride the gossamers That idles in the wanton summer air, And yet not fall, so light is vanity. (2.6.16-20)
When Juliet rushes into Friar Laurence's cell to marry Romeo, the Friar makes a big deal about the fragility and fleetingness of worldly pleasure (a young lover's "vanity"). But (of course) there's another meaning: Stephen Greenblatt tells us that, when Friar Laurence says Juliet's "light" foot won't "wear out the everlasting flint," he means that she will never "endure or subdue the hard road of life" (source).
FRIAR LAURENCE These violent delights have violent ends And in their triumph die, like fire and powder, Which as they kiss consume. The sweetest honey Is loathsome in his own deliciousness And in the taste confounds the appetite. Therefore love moderately. Long love doth so. Too swift arrives as tardy as too slow. (2.6.9-15)
The Friar, who is worried about the long-term consequences of Romeo and Juliet's marriage, warns Romeo that his and Juliet's intense passion may end suddenly and violently, like the flash of gunpowder. And, yep: that about sums it up for us.
Act 3, Scene 5
JULIET Wilt thou be gone? It is not yet near day. It was the nightingale, and not the lark, That pierced the fearful hollow of thine ear. Nightly she sings on yon pomegranate tree. Believe me, love, it was the nightingale. (3.5.1-5)
Juliet denies the passing of time (made evident by the sunrise and the sound of the morning birds twittering) because she knows that the passing of time means that Romeo's going to have to jet. Brain Snack: this kind of poem is called an "aubade," or "morning song."
Act 5, Scene 3
JULIET 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 die with a restorative. (5.3.166-171)
Juliet thinks suicide will let her be with Romeo forever, which… well, whether or not this is true depends on how you feel about the afterlife.