As Shakespeare's Romeo and Juliet is a play of contrasts and extreme emotions, the soliloquy of Friar Lawrence underscores these motifs:
For naught so vile that one the earth doth live,
But to the earth some special good doth give;....
Virtue itself turns vice, being misapplied,
And vice sometime's by action dignified (2.3.17-21)
The friar's reflection that extremes of any kind are dangerous proves to be true in many instances throughout the play. For instance, Romeo's impulsive act of climbing into the Capulet orchard in hopes of seeing Juliet is mortally dangerous; the well-meaning, but also impetuous act of the priest in marrying the young lovers in the hope of ending the feud backfires as Juliet later cannot marry Paris as her father demands. This situation, of course, leads to Juliet's desperate act of pretending to be dead and being placed in the catacomb, which in turn leads to Romeo's misjudgment of her condition and his death as well as hers.
Certainly, Romeo's extreme love for Juliet clouds his judgment when he encounters the disputing Tybalt and Mercutio. Because he loves Juliet so much, Romeo does not reason well in Act III and be more defensive in his encouter with Tybalt. Then, when Mercutio is killed and Romeo slays Tybalt in revenge, an extreme act of hate, an action which leads to his own demise.