曾经说好了生死与共
[céng jīng shuō hăo le shēng sĭ yŭ gòng]
Translating to 'Once we agreed to share life and death,' this conveys a past agreement or promise between the user and another to face difficulties and challenges together no matter what, implying strong loyalty, deep friendship, or committed love that was perhaps made in earnest moments of connection.