How does the suicidal impulse that both Romeo and Juliet exhibit relate to the overall theme of young love?
The young lovers' "all-or-nothing" impetuous behavior is consistent with the suicidal impulses of Romeo and Juliet. Impulsive is appropriate to much of the action in "Romeo and Juliet." For instance, Romeo sees Juliet and immediately ends his melancholic sighs over Rosalind. Then, he impulsively races to Friar Laurence to ask to be married Juliet, whom he has only know for hours. After he unwisely comes between Mercutio and Tybalt causing Mercutio's death, Romeo madly stabs Tybalt. Again, he rushes to Friar Laurence, flings himself down, crying and pulling out a dagger to kill himself until the priest reasons with him. Finally, when he mistakes Juliet for dead, he does not leave the tomb to consult with anyone before killing himself.
In the same manner, Juliet runs back and forth impulsively and indecisively in the balcony scene. When her parents insist that she marry the prince, Paris, Juliet says that she will seek the counsel of the Friar, and if "all else fail, myself have power to die." Like Romeo, Juliet sees only one choice to take if she does not have things the way she wants. Later when the Friar has a vial of a liquid which should make her appear dead, and Juliet is worried about the drug actually killing her, she still drinks it and places a dagger beside her in case all else fails.
R and J are as fickle as the Fortune that seems to dictate their destinies.