I have been going to Recovery International meetings to learn some CBT to deal with it. In RI, negative self talk is called fearful temper. It sounds silly, but having these short "spots" to mentally repeat helps a lot. You generally begin by recognizing how average, not exceptional, what is happening is; "trivialities" is the RI term. Then there are a huge number of various phrases that help you approach things better. "Interpret securely, don't exaggerate insecurely" applies to my negative thinking a lot. I am not that skilled in it yet but it is helping. If there is a meeting near you, I encourage you to check it out.