What does it mean to have a Cassandra personality?

I heard the saying today but wasnt sure what it meant exactly. It was in the context of “you have what is called a Cassandra personality”. I have googled it but not really come up with anything much. What does it mean? I know she was a greek mythology character but how does that transcribe into nowdays and someone being said to have or be a Cassandra personality. Is it real or is it a sort of joke? What would be the traits of this kind of character and what references or similar characters are there in literature inspired by the Cassandra personality?