Romeo pronounces these words right after having mortally wounded Tybalt, guilty of having just killed Romeo’s friend Mercutio. In a fit of rage, Romeo takes his sword and attacks Tybalt ferociously, killing him. This is the climax of the play, that will change inevitably the destiny of the two ‘star-crossed lovers’. Romeo realizes what he has done, now he knows he has to pay the consequences of his deed, his already dangerous love for Juliet is going to cause a compulsive chain of tragic events, bringing the two lovers to certain death.
He defines himself as a puppet of the unpredictable destiny.
Even from the opening lines, the audience is informed about the tragedy that is going to affect the two protagonists, establishing fate as a theme at the foreground of the play. The idea that tragic circumstances were decided from birth for these two lovers is suggested: ‘from forth the fatal loins’ (I.i.5). This line together with, ‘a pair of star-crossed lovers take their life’ (I.
i.6) explains to the audience that destiny was what first brought them together and is what will eventually separate them. The Chorus’s opening speech is continually echoed throughout the rest of the play by other characters making direct references to fate. As Susan Snyder states: tragedy can be seen as a ‘ritual sacrifice’, in which the protagonist is ‘both hero and victim, […], separated from the ordinary, but destined for destruction.’ 
Even though Romeo defines himself as helpless victim of his “fortune”, there is much evidence of the important roles that Romeo and Juliet have in shaping and, in many cases, worsening, their destiny. After a careful reading of the play we can state that it is not just a question of destiny. Romeo and Juliet would have been able to save their relationship simply by using more acuteness, composure and resolution. ‘The choice of means confronting Romeo and Juliet is not confined to a single occasion, they are given a series opportunity of choice’  , but unluckily they always seem to choose the wrong way in which to direct their story.
Again we find a metaphor relating to the stars, as if Shakespeare has chosen these celestial bodies as symbols for the fatality that lies over the whole play. But here we find the first of Romeo’s mistakes, he takes a decision without thinking of the consequences: he has read the list of guests that are going to be at the feast and although he is informed about the presence of Capulets, Montague’s arch-enemies, he decides to attend in any case. As already mentioned, Romeo kills Tybalt out of rage, even though he knows it makes things all the worse for his current situation with Tybalt’s cousin, Juliet; but a far more basic instinct, the desire of a man to avoid being thought a coward prevails and Romeo is driven to fight Tybalt.
While Romeo lacks composure, Juliet’s flaw is impetuosity. During the balcony scene, Juliet hurries Romeo into marriage by constantly questioning his love for her and saying things like, ‘If thy purpose marriage, send me word tomorrow’ (II.i.143-4). The Friar’s flaw, which in the end had a big effect on this tragedy, is to be too impulsive. He offers to marry Romeo and Juliet, even though he knows there is a huge conflict between the families, probably hoping that the marriage would have solved all the rivalries. Moreover, we must remember that it is the Friar who gives Juliet the potion for suspended animation, which aggravates things even more.
Even though the protagonists share many ‘fatal defects’, lots of things happen to their misfortune that is not their fault. First of all, Romeo and Juliet shared the unfortunate fate that they were from feuding families, putting their relationship in jeopardy from the beginning. Juliet expresses well this idea in her soliloquy on the balcony: ‘What’s in a name? That which we call a rose, by any other word would smell as sweet […]” (II.i.86-87). A second strike of bad luck is the fact that the Capulets, being a typical upper-class traditionalist family, had arranged a marriage between Juliet and Paris, against the will of their daughter.
The scene in which Romeo finds out about the feast is another twist of fate. The illiterate servant of Capulet’s was given the job of telling people about the party. Since he could not read, he was forced to ask two strangers to explain it to him. Those two people could have been anyone, but they just happened to be Romeo and Benvolio. Another ironic fact is that Romeo went to the party because he was madly in love with Rosaline. If Rosaline had been there, and she returned Romeo’s love, then all the following suffering would never have occurred. Romeo was completely in love with another woman going to the party, which he only found out about in the first place through an adverse stroke of luck. Another example of bad luck is that Romeo never received the letter of Friar Laurence informing him about his and Juliet’s scheme because of the plague in Mantua, the city where Romeo went to stay after his banishment from Verona. The letter must reach Romeo in time so that he knows of the arrangement between Juliet and the Friar, but the city has been put under quarantine because of a plague. So Romeo never receives the letter and he is left unaware of the plan between the Friar and Juliet:
Again we find the concept of fortune. The Friar curses this fate, the ‘unhappy fortune’, aware that the story of the two lovers has probably came to an end. Romeo is told by Balthasar that Juliet has died: ‘Her body sleeps in Capels’ monument, and her immortal part with angels lives’ (V.i.18-19). These events are the last straw and they will lead to the demise of both characters.
Obviously the fate is closely related to the concept of time. Timing, in fact, played the largest role in deciding if they would live or die. Many scholars have defined it as the ‘lover’s enemy’, which retards ‘his pace when the lovers are separated and accelerates it when they are together’: 
‘O lamentable day! O woeful time!’ (IV.iv.57)
In the balcony scene Juliet hurries because the Nurse is calling her; if Romeo had arrived a few minutes later at the tomb, the tragedy would not have happened; moreover, if the wedding of Juliet and Paris had not been brought forward from Thursday to Wednesday the letter would have had more time to reach Romeo in Mantua; if the Friar had entered the tomb earlier he could have explained the situation to Romeo and no harm would have happened to anyone. These are only a few examples of the negative and mysterious force that seems to control the happenings.
We can definitely say that Romeo and Juliet is a crossing of fortuitous events, coincidences and personal responsibilities, all masterfully managed by fate and time. The love story did not have to begin, the two lovers were not meant to meet each other, son and daughter of rival families. They both knew this, but they could not accept it, their love was bigger than anything else. What if it was the temptation of the forbidden which increased their love? Two teenagers, two rebels living in a sexist society made of wedding vows and past rivalry. They preferred to risk, but risking is a matter of fate, a cruel fate which brought them to a certain death. As said by Cassius in Shakespeare’s Julius Caesar  , ‘The fault, [â€¦], is not in our stars but in ourselves’ (I.ii-139-40).