The death of the two infatuated lovers is truly tragic and illustrates how impetuousness can lead to rash decision-making with disastrous consequences.
Because Romeo and Juliet were caught in the feud between their families, it was apparent that their relationship would face some difficult obstacles that they had to overcome. They naively believed that their secret marriage would be the salve to heal all wounds, as the friar stated:
...For this alliance may so happy prove,
To turn your households' rancour to pure love.
But it was not to be. The decision proved to be much too impulsive because firstly, Romeo was banished at the risk of death from Verona for killing Tybalt and, secondly, Juliet's father, Lord Capulet, practically forced his daughter to marry Paris. She could obviously not tell him that she had already been wed and sought advice from the friar.
Friar Laurence, for his part, suggested that she drink a potion which would render her so completely unconscious that it would be assumed that she had died. She would then be interred in the family burial vault, where Romeo would later come to rescue her. An urgent message would be sent to Romeo in Mantua informing him about the details of the plan.
It is unfortunate that Romeo never received the message. Fate intervened and the messenger was unable to complete his task. Romeo heard of Juliet's unfortunate "demise" from Balthasar and decided to take his own life by drinking a powerful potion prepared by an apothecary. He would join his beloved Juliet in her tomb and then ingest the poison and meet his fate next to his love.
After an encounter with Paris outside the tomb in which he killed the unfortunate prince, Romeo entered the sepulcher, saw what he believed was his dead love, and took the poison. He died soon thereafter. Juliet recovered from the effects of the poison when Friar Laurence, on a mission to intervene, had just entered the tomb. The friar urged her to leave the tomb but she refused and decided that life without Romeo had no purpose. She took Romeo's dagger and fatally stabbed herself.
In the end, the lords Capulet and Montague realized the folly of their purposeless feud and decided to end it. The two families had lost their loved ones and finally understood that their battle caused unnecessary strife and should cease. Both families decided to erect a monument in memory of the two doomed lovers and as a reminder.