Recall past sufferings and today's happy life. It refers to what you have experienced, knowing how you feel, and it is not appropriate for others to say it.

"Remembering bitter thoughts is sweet, knowing oneself in cold and warm" comes from: Xin Li's "Old talk. Making up village history": "Appearing in person, vivid and concrete, remembering bitter thoughts is sweet, inviting and thoughtful."

It is an idiom to recall the pain of being oppressed and exploited in the old society. It is hard to live a happy life in a new society; Thereby improving ideological awareness. From Deng Xiaoping's "Speech at the Political Work Conference of the Whole Army": "Of course, it is necessary to recall bitter thoughts and sweet thoughts, but it is not enough to just recall bitter thoughts and sweet thoughts. It is necessary to study how to improve the political consciousness of soldiers under the new historical conditions."

Self-knowledge of cold and warm, originally refers to the cold and warm of water, and the drinker knows it. Zen Buddhism is used to describe the realm of self-enlightenment. It is also a metaphor for the depth of learning experience, only oneself know.