Mine, right now, just keeps repeating "Everything sucks. You suck. You need to find a way to escape this drudgery."
This is not productive. It is not good for my mental health. But I can't stop.
I can't stop because my brain's telling me that if I stop, I'll settle. I'll become OK with the status quo, and that's not acceptable.
I think that mentally healthy people either have positive thoughts running through their head when otherwise unoccupied, or absolutely nothing at all (hello zen masters).
But this is my idle loop now. I'd like to change it, but the part of me that knows that there must be something more to life rejects my attempts. It's not gonna allow a change unless the new thought is compatible with who I want to be.