In the Prologue to Act II, the Chorus continues the theme of paradoxes: old desire/young affection, deathbed/heir, foe/lover, extremities/extreme sweet. With these paradoxes, the allusion is to the extreme efforts to which Romeo and Juliet go in order to be together.
Romeo's being a foe of Juliet's family, the Capulets, may not give him "access" to her as nor may Juliet be able to see him since she has
means much less/To meet her new beloved any where (II,i,)
But, the Chorus states, their passion "lends them power" to meet each other and they will go to extremes to be together, "extreme sweet," in each other's arms.
Of course, Romeo and Juliet do just that. Romeo scales the walls of Juliet's orchard--"he jests at scars"--despite the obstacles of trees and branches. When Rome tells Juliet "I would I were thy bird," she replies,
Weet, so would I:/Yet I should kill thee with much cherishing./Good night, good night!parting is such/sweet sorrow,/That I shall say good night till it be morrow(II,ii,182-185)
The line "Yet I should kill thee with much cherishing" foreshadows, of course, the tragic end of Romeo and complements the paradox of the deathbed as well as that of foe/lover in the Prologue.