People dream that they are under too much pressure, or watch related movies and books during the day. Some people are bullied by their bosses, but they can't get angry. In the evening, they dreamed that a person was severely beaten by a group of thugs, so they comforted themselves that the person who was beaten was the boss and the group who beat him was their own anger.
Or watch too much during the day. After seeing a detective Conan, I slept and dreamed that I was going to dig a grave.
In short, it doesn't matter what you dream. If you are superstitious, dreaming of blood also means that we are lucky! relax ...