时光好狠总想把我们分开
[shí guāng hăo hĕn zŏng xiăng bă wŏ men fēn kāi]
This means 'Time is so ruthless that it tries hard to tear us apart', implying that fate tends to create many obstructions and challenges for them and eventually separate couples. People tend to choose such nicknames when reminiscing over the past, mourning lost love, or missing a former friendship.