People are cold and cold, and they know their warmth and coldness. What does it mean?

The meaning is: People's hearts are cold, and people are selfish creatures. They only care about their own emotions and not others, so they can only care about themselves.

Perhaps everyone spends most of their time and energy on others in their life, but in the end, they get nothing, so don’t always think about being polite to others, but be selfish. Pay attention to whether you are unhappy or sad.

If you don’t care about your own warmth or coldness, then how can others care? So caring for your body and emotions is the most important thing.