We smile and function in the world at large, few ever guessing at the brooding thoughts branching inside us, choking our breath sometimes, making us shake, yet somehow, the terrible things we are capable of imagining almost never come to be. (I went back and added the word "almost" in that sentence, wary of challenging the fates.)
I remember a woman saying years ago that you can't stop disquieting thoughts from showing up. Like birds they alight before our peripheral vision can detect their flight. But if we can't always prevent their arrival, this woman said, we can keep them from building nests in our heads.