How are Juliet's circumstances tragic in Romeo and Juliet?

There are many tragic circumstances that apply to Juliet's life in Shakespeare's tragedy Romeo and Juliet. One of these tragic circumstances is her relationship to her parents. She is a member of the nobility, and as such, is raised by a nurse rather than her parents. When she does have occasion to see her parents, she is expected to be completely malleable to their will and show total obedience to them. This is evidenced in Juliet's response to her mother when she tells Juliet of Paris's marriage proposal. Juliet replies to her mother's question of whether or not she'd like to marry Paris by saying "I'll look to like, if looking liking move, but no more deep will I endart mine eye than your consent gives it strength to fly." (Romeo and Juliet, Act I, Scene III) In this speech she is saying she will look at Paris to see if she will like him romantically, but she won't look any more (or less) than her mother would like. Later on, her father disowns her for refusing to marry Paris. This shows that her worth to them was not so much as a beloved daughter but as an obedient pawn who would strike a good marriage to further their own wealth, influence, and esteem. 

Another tragic circumstance, of course, is that the young man she falls in love with happens to be the sworn enemy of her family. There is no likelihood at all, despite Romeo and Juliet's young and foolish imaginings, that either of their parents will ever consent to their match. 

Because of her young age and subordinate position as a woman during Renaissance times, she would not have been able to run away with Romeo, or follow after him when he is banished, making her a prisoner of her circumstances, which is certainly tragic. Women were not able to travel alone, be seen with a member of the opposite sex unchaperoned, or own property, and they were subjected to many other rules as well. 

Juliet accepts the Friar's plan and takes an herbal potion that will slow her heart rate and breathing to give the appearance of death in a desperate attempt to be with the one she loves. Tragically, the message that is sent to Romeo to let him know of the plot never reaches him, another way in which Juliet is a victim of tragic circumstances. They relied on a messenger to get the message to Romeo in a neighboring town, but the messenger was prevented from reaching him by a quarantine.

When Romeo finds Juliet and thinks her dead, he takes a deadly potion he received from an apothecary. She finds him dead when she awakes. She can find no reason to live in a world in which her love is gone, which is tragic, and uses his dagger to end her own life. 

Lastly, the bitter irony is that with the deaths of Romeo and Juliet, the families who had feuded for so long are able to make some peace with each other. If they'd been able to put aside their pride while Romeo and Juliet yet lived, the ending would have been quite different.