@witsend000, from reading what others have said, I came up with these suggestions:
- Don’t overthink it. Write as it comes to you, negative or otherwise. The key point is not to edit yourself.

But I can understand your concern about perpetuating negative thoughts or feeling, so why not try:
1. Reflect on the event you wish to write about and intentionally reflect on the things you liked or appreciated about the event.
2. Start a gratitude practice. Even on the days when you need to vent and purge the negative, end with one thing you remain grateful for.

What do you think? Doable?