What are some quotes about tragic love from Romeo and Juliet?

Here are a few lines of text that you may find helpful. 

ROMEOLove is a smoke raised with the fume of sighs;Being purged, a fire sparkling in lovers' eyes;Being vexed a sea nourish'd with loving tears:What is it else? a madness most discreet,A choking gall, and a preserving sweet. (I.i.197-201)

In this passage, which is spoken by Romeo early in the play, Romeo talks of naive and innocent love, which...

Here are a few lines of text that you may find helpful. 

ROMEO
Love is a smoke raised with the fume of sighs;
Being purged, a fire sparkling in lovers' eyes;
Being vexed a sea nourish'd with loving tears:
What is it else? a madness most discreet,
A choking gall, and a preserving sweet. (I.i.197-201)

In this passage, which is spoken by Romeo early in the play, Romeo talks of naive and innocent love, which often feels tragic. Romeo does not describe love as a pleasurable thing, but instead as a "madness most discreet" and a "choking gall." At the very start of the play, Shakespeare intentionally sets up love as tragic.

JULIET
Well, do not swear. 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.
Good night, good night. As sweet repose and rest
Come to thy heart as that within my breast. (II.ii.123-131)

Here, Juliet confesses that she experiences joy in the blossoming love between Romeo and herself, but she is worried it is "too rash, too unadvised, too sudden." Shakespeare provides warning signs throughout the play that this love will end in tragedy. This speech is an example of this foreshadowing technique.  

ROMEO
How oft when men are at the point of death
Have they been merry, which their keepers call
A light'ning before death! O, how may I
Call this a light'ning? (V.iii.88-91)

In this speech, which Romeo gives before his death, Romeo trades death for his love, Juliet. He describes how miserable he is before death and how he is willing to die in order to be with Juliet. This is the pinnacle of the tragic love in Romeo and Juliet.