You can change your dream content and mood:

How to Control Your Dreams: 9 Steps (with Pictures) - wikiHow

I find for myself, I do not watch TV (most shows are too stimulating or violent or negative in some way).

Instead I read, or work on my art in my head before falling asleep.
I find Alexander McCall Smith books very soothing and helpful
for initiating sleep and nicer dreams.

I had a very painful dysfunctional childhood and it has been a lifelong task to put that to rest. It takes effort and letting go of the past which are tough tasks but can be done. I also found self hypnosis helpful, which I did for improving my imagery for my art, but it also helps with pain, and depressive thoughts too I found.

I found this book while on a trip to New York City in the 70's.
You can get it used on Amazon still today.
Seeing With The Mind's Eye: The History, Techniques and Uses of Visualization: Michael Samuels, Nancy Samuels: 978394731131: Amazon.com: Books
This book was very helpful for me to open doors to increased creativity and also teaches relaxation and a form of self hypnosis.

I truly believe that TV before bed can be too arousing and often it goes straight to the unconscious mind, to arrive in one's dreams. This also goes for disturbing news shows, etc.