Answer: Romeo's impulsive nature leads to the tragic ending of the play.
Explanation:
In this excerpt from Act II, Scene II, Juliet describes Romeo's actions as "too rash, too unadvised, too sudden." Romeo jumps the Capulets' wall to confess his love for Juliet and propose to her. As this happens on the eve they met, Juliet claims that Romeo is rushing into revealing his feelings, and is afraid that this would have a negative impact on their relationship. In this particular excerpt, Juliet compares Romeo's actions to lightning, "which flashes and then disappears before you can say..." It turns out that she was right - Romeo's impulsive nature leads to their death. At the end of the play, he impulsively reacts when he finds out that Juliet is dead, and kills himself before the Friar has a chance to tell him she is, in fact, alive.