《礼记·曲礼上》
对于自己所喜爱的人，不可只知其优点，而不知其缺点；对于自己所憎恶的人，不可只知其缺点，而不知其优点。
爱而知其恶，憎而知其善。积而能散，安安而能迁。
For the people you love, you should not only know their advantages, but also know their disadvantages; For the people you hate, you should not only know their disadvantages, but also know their advantages.