I think about this too sometimes. It's an anxiety... like a voice in the back of my head is telling me that it's going to happen.
I think it's a normal fear, especially for us that have gone through depression and/or trauma.
The thing that keeps me going, though, is that there is always hope. There are so many stories out there about people who got through it, who turned things around, who fought and were able to prevail. Why can't we be like those people? There is nothing that makes us different. We all share the same DNA, and we all have a chance.