Benvolio: tut! man, one fire burns out another’s burning, one pain is lessen’d by

Benvolio: tut! man, one fire burns out another’s burning,
one pain is lessen’d by another’s anguish;
turn giddy, and be by backward turning;
one desperate grief cures with another’s languish:
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take thou some new infection to thy eye,
and the rank poison of the old will die.
according to benvolio, what will cure romeo’s heartache?