What does it mean to lose a star in the constellation?

This is a fortune-telling term. The so-called "Sangmenxing" is a symbolic constellation that brings bad luck to people, just like the "broom star". The whole meaning of this word is:

Look at the sky. You are destined to be a Sang Men star this year, and your bad luck will continue. I suggest you try to overcome it!

The fortune teller tricked you into buying it. Man's fate is not necessarily related to the stars in the sky! Please don't believe it.