How to make GPT forget the first prompt

If you had an ongoing session in playground, how would you get it to stop writing about the first prompt, and work on the next one, or would it be better just to start a whole other session? I have tried saying, “Stop talking about _____ and start talking about ____” but that and similar prompts haven’t worked.

Could you give an example of what you’re trying to do?

I was writing something for my bar mitzvah, and I wanted it to keep the mood the same throughout the responses that GPT would give me. For the first part it worked, and wrote a really good paragraph about Autumn, but, no matter what instructions I gave it, when I wanted it to switch to write about mythology, it wrote a tiny bit, and then kept bringing Autumn up.