I had a nightmare. In my dream, my mother was killed by someone else. I was very sad and had a dream.

Generally speaking, you need to relax at first, and don't care too much about dreaming. It is not advisable to think about problems or read books between half an hour before going to bed and 1 hour. You should do proper physical activities to avoid nervous mental activities. Pay attention to have a good rest and develop good living habits.