We don't need to bother with a spoiler alert, because Shakespeare wants us to be spoiled. It goes out of its way to tells us that Romeo and Juliet are destined for tragedy: in the opening Prologue, we learn that the "star-cross'd lovers" will "take their life." At the same time, there's still a sense that Romeo and Juliet decide all on their own to commit suicide—not to mention, there are plenty of players (the meddling Friar and Nurse, Romeo and Juliet's warring parents, etc.) who contribute to the play's tragic events. In Romeo and Juliet, maybe "fate" is just another word for "consequences."
Romeo and Juliet have no control over their tragic destinies—they're simply victims of fate.
In Romeo and Juliet, individuals bring about their own fates.