The main idea of the quote is to bring out the idea that no one really wins in an intense rivalry. Rather than awarding one side "the winner" in a competition of such intense magnitude, the third path of seeing both sides as losing is the underlying idea of the quote. The idea of a "plague upon both houses" reflects how each side is as fundamentally bad as the other. It is here where I think that the ending to the drama supports the idea of a "plague upon both houses." This is seen in the Prince's speech at the end of Act V. Both houses end up bearing striking similarity to one another of the narrative. Each has lost a child to suicide. Each struggles to make meaning of the loss. Each house cannot fathom why their beloved felt compelled to take their life. The "plague" on both houses is the fundamental struggle of understanding how their hatred and enmity could lead to the death of a beloved child. It is here where the quote is felt the strongest. The Prince brings this out in suggesting both Capulet and Montague are to blame for their child's death. It is at this moment where the quote's sentiment is felt the strongest.