Pessimism or something else?

I’m not sure if this is the right place to post this, maybe should be in depression or personality disorder, even OCD. I put it here because I think my PTSD is the root of it all. I’d like to know if anyone else here does this.

Without getting into details, basically my life was very ugly and empty since I can remember. Many years later, things are finally turning around. I can actually say I have a good life, job, home, family. I feel really good some days. I still have depression, and I know that will take some time because I’m still working through stuff. But like even when I’m not depressed or having a memory, I might be having a great day, but it’s like my mind wants to be sad. This really bothers me. I’m trying to figure out if I’m just a pessimist, masochist, if it’s part of my personality, if it’s a trait of the personality disorder, if it’s obsessive thoughts, if it’s just an effect of PTSD trying to be ready for the worst, if it’s mood disorder, or if it’s self-harm punishing myself. I even wondered if it’s an addiction, chemically in my mind, like I’m so used to being sad that I have withdrawals when I’m finally not sad.