What does it mean for a person to say that his four pillars have fallen down before he dies?

There are several eight characters in the folk tradition, which are the five elements of the year, month, day and hour when a person was born, and the four pillars are eight characters, such as B Wei (year), Shen Jia (month), Xin Mao (day) and Ren Chen (hour), which are the "eight characters" of people born at this time. Four pillars fell, of course, is dead.