The deaths of Romeo and Juliet were tragic for several reasons, but to name a few: the deaths didn't have to happen. Had they explained to their parents that they had married one another secretly, it would not have been pleasant, but no one would be dead. They are also so very young. Any time a young person takes his or her own life, it is very tragic indeed. In addition, they had two adult allies, and neither of them stepped up to speak on behalf of the young couple. So, the Friar and the Nurse have these two deaths on their heads as well. Also, it is very sad that so many things went wrong which could have prevented the whole catastrophe: the note from the Friar to Romeo wasn't delivered in time, Romeo thinks Juliet is truly dead, and he kills himself in the tomb; the Friar arrives too late to keep Romeo from doing the act, and also to prevent Juliet from killing herself. On top of it all, the Friar's poor timing not only allows Romeo time to kill himself, but also Paris. So, there are three young people slain in the tomb of the Capulets by the end of Act V. It is all so senseless and sad.
While Romeo and Juliet do not fit the classic definition of tragic heroes, as defined in Aristotle's Poetica, who come in conflict with ethical forces, they do possess the tragic flaws of such classic heroes. This hormartia is more correctly defined as not a flaw, but a mistake. Certainly, Romeo makes the mistake of telling the fiery Tybalt that he loves him now that he is a "cousin" and Tybalt misinterprets this gesture as a mockery. Likewise, Juliet mistakenly agrees to follow the erring Friar's suggestion to feign her death, leading to Romeo's grave personal mistake, as well.
The death of these two star crossed lover was tragic mostly because of the reason that it didn't have to happen that way. For example, if the two households ( Montague and Capulet ) didn't have such a feud between them , the two lover could have ended up together alive .
She drank posion and killed herself.