I've heard this advice all my life, and if you're interested in writing, I'm sure you've heard it, too. "Write what scares you," as in, go to the dark places your mind wants to avoid. Tell those traumatic stories. Dig deep into the bad, negative, scary.
Which is... fine. Yes, it's important to speak up and speak out and let your voice be heard as a writer. But I think considering the opposite advice is equally relevant. How about, "Write what makes you happy?"
By "happy," I don't necessarily mean bouncing off the walls with joy. I mean think about how the work makes you feel while you're in it. Aim for a focused, in-the-zone feeling, and you'll have a good experience creating your work. The end product won't always be upbeat, but that's not the point. "Happy" writing is about the process for the writer, not the final written piece and not the readers' feelings about it.
When you write, you have to live in the space of your chosen topic. A "scary" topic for you may mean spending an awful lot of time in head space you'd rather avoid. Why do that to yourself? You're under no obligation to go there if you opt out.
Writing doesn't have to be an exercise in mental torture - or therapy - for the writer. Your work isn't more valid or better just by virtue of focusing on topics that trouble you. Feeling good while you write is a part of taking care of yourself and your creativity.
For more on this and other writing-related topics, listen to my podcast Better Life, Better Writing.