See in text (Act IV - Scene V)
Here, Capulet personifies Death to suggest that Juliet was a victim. None of the characters seem to believe that she killed herself. In personifying Death, they are able to construe Juliet's death as a random act of chance.
"For fear of that..."
See in text (Act V - Scene III)
Romeo fears that Death will keep Juliet as his love, and thus vows to kill himself to protect her from Death. Romeo personifies Death here in order to offer a reason why he must die other than sadness over Juliet's death. If Death is a personified being, then Romeo can protect his love from this "abhorred monster."