All is fair in love and war

ai5 kɪŋtuː hɛtuː ʒanfɔː ts.ə5ŋ ts.onɡ5 jɪwɒn kiːfɔː dʒiːwɒn jaʊθɹiː kɛθɹiː nɛŋtuː

In Chinese 爱情和战争中，一切皆有可能。

This idiom is used in Chinese to express that the rules are different in love and war.