The theme of impulsiveness and its consequences that could have otherwise been avoided is demonstrated all throughout the play Romeo and Juliet.
The first instance of impulsiveness that we see is Romeo's decision to join his friends in crashing the ball given by the Capulets in. At the ball, Tybalt sees Romeo and feels insulted by his presence. Tybalt asks himself if Romeo has come to laugh at their party in the line:
What, dares the slave
Come hither, cover'd with an antic face,
To fleer and scorn at our solemnity?(Act 1, Scene 2)
Tybalt's feeling of insult, coupled with Lord Capulet's refusal to let Tybalt fight Romeo, makes Tybalt promise to revenge himself on Romeo, which ultimately leads to both Tybalt's and Romeo's death. Hence, had Romeo not made the impulsive decision to crash the ball, Romeo would have remained alive.
A second instance of impulsiveness is seen in Friar Laurence's decision to marry both Romeo and Juliet. Friar Laurence believes that Romeo is not truly in love, nor does Romeo truly know what love is, as we see in the line, "Young men's love then lies / Not truly in their hearts, but in their eyes" (Act 2, Scene 3). Furthermore, he believes that their decision to marry is far too hasty, as we see in the line, "Wisely and slow; they stumble that run fast" (Act 2, Scene 3). However, Friar Laurence makes the impulsive decision to cater to both Rome and Juliet's equally impulsive whimsies by agreeing to marry them. His motive is that uniting the two lovers will help put an end to their families' feud. However, while Friar Laurence's plan did put an end to the feud by the end of the play, the impulsive plan went awry, causing the death of Romeo, Juliet, and even Paris.